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Cabochon is a gem cutting term referring to a gemstone cut so as to have a domed upper surface. Formerly the term refered to gems which were polished, but were uncut.
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Cabrerite, named after the Sierra Cabrera, Spain, is an apple-green mineral, a hydrous arsenate of nickel, cobalt, and magnesia.
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Cacholong or mother-of-pear opal and sometimes Kalmuck agate, is a variety of opal, usually grey in colour, milk white or bluish white, and resembling mother-of-pearl. It is banded with layers of different colours and is a most attractive ornamental stone.
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Cacoxene is a hydrous phosphate of iron occurring in yellow radiated tufts. The phosphorus seriously injures it as an iron ore.
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Cadmia is an oxide of zinc which collects on the sides of furnaces where zinc is sublimed. The name was formerly applied to the mineral calamine.
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Caen-stone is the French equivalent for the Bath stone or oolite of England. It is a cream-coloured building-stone of excellent quality, obtained near Caen in Normandy. Winchester and Canterbury Cathedrals, Henry VII's Chapel at Westminster, and many churches are built of it.
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Cainozoic is a geological term applied to the latest of the three divisions into which strata have been arranged, with reference to the age of the fossils they include. The Cainozoic system embraces the tertiary and post-tertiary systems of British geologists, exhibiting recent forms of life, in contradistinction to the Mesozoic, exhibiting intermediate, and the Palaeozoic, ancient and extinct, forms. It corresponds nearly with what has been called the age of mammals.
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Cairngormstone is a yellow or smoky brown variety of rock crystal, or crystallized quartz, found especially around the mountain of Cairngorm, in Scotland.
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Calamine is the common name of two zinc ores - one being a hydrous silicate also known as smithsonite, hemimorphite, or electric calamine; the other being the carbonate. Both occur frequently in veins which carry zinc blende, the commonest of the zinc ores. They are pale yellow, pink, brown, blue, green or colourless and are often mixed in a fine powder known to miners as ' dry bone'. Calamine is used in medicine as a skin soother to relieve rashes and other skin irritations.
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Calaverite is a bronze-yellow massive mineral with metallic lustre; a telluride of gold. It was first found in Calaveras County, California.
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Calc-sinter or calcareous tufa is a loose and porous deposit of carbonate of lime, formed by mineral or petrifying springs. Water charged with carbonic acid can dissolve carbonate of lime out of the rocks, and on its emerging to the air, deposit part of it again in the form of an incrustation.
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Calcareous refers to containing calcium carbonate or calcite.
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Calcic refers to containing calcium.
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Calcite is a common mineral composing such rocks as chalk and marble. It has the formulae CaCO3 and a relative hardness of 3. It effervesces vigorously with HCl. Clear specimens exhibit double refraction. Occurs as widespread sedimentary rock masses such as limestone. Crystalline metamorphosed limestones are called marbles. Argentine is a pearly lamellar variety; aphrite is foliated or chalklike; dogtooth spar, a form in acute rhombohedral or scalenohedral crystals; calc- sinter and calc-tufa are lose or porous varieties formed in caverns or wet grounds from calcareous deposits; agaric mineral is a soft, white friable variety of similar origin; stalactite and stalagmite are varieties formed from the drillings in caverns. Iceland spar is a transparent variety, exhibiting the strong double refraction of the species, and hence is called doubly refracting spar.
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Caledonite is a hydrous sulphate of copper and lead, found in some parts of Caledonia (Scotland).
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Caliche is the name given to naturally occurring crude sodium nitrate found in Chile. Caliche contains from 20 to 50 per cent sodium nitrate and also traces of sodium iodate.
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The Cambrian period was the third geological period, 450,000,000 years ago.
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Canary stone is a yellow species of carnelian, named from its resemblance in colour to the plumage of the canary bird.
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Cancrinite, named after Count Cancrin, a minister of finance in Russia, is a mineral occurring in hexagonal crystals, also massive, generally of a yellow colour, containing silica, alumina, lime, soda, and carbon dioxide.
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Candite is a variety of spinel, of a dark colour, found at Candy, in Sri Lanka.
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Cannel Coal is a dull black coal which breaks with a conchoidal fracture and does not soil the fingers when handled. In some respects it resembles jet. It is easily cut, and will take a high polish. It contains a large proportion of volatile constituents making it suitable for gas manufacture, and it burns with a bright white flame.
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In geology, the Caradoc sandstone is an upper division of the lower Silurian rocks, consisting of red, purple, green, and white micaceous and sometimes quartzose grits and limestones containing corals, mollusca, and trilobites. Named after the hilly range of Caer-Caradoc in Shropshire.
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Carbonaceous refers to composed chiefly of organic carbon. (i.e. carbon derived from plant and animal remains.)
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Carbonado is a black variety of diamond, found in Brazil, and used for diamond drills. It occurs in irregular or rounded fragments, rarely distinctly crystallized, with a texture varying from compact to porous.
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Carbonates refers to minerals, such as calcite, where the carbonate radical (CO3) is an important constituent.
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In geology, the Carboniferous was the seventh geological period, 250,000,000 years ago. This era marked the formation of the coal beds. It is the great group of strata which lie between the Old Red Sandstone below and the Permian or Dyas formation above, and is named from the quantities of coal, shale, and other carbonaceous matter contained in them. They include the coal measures, millstone grit, and mountain limestone, the first being uppermost and containing the chief coal-fields that are worked. Iron-ore, limestone, clay, and building-stone are also yielded abundantly by the carboniferous strata which are found in many parts of the world often covering large areas. The thickness of the coal measures in South Wales has been estimated at 10,000 to 13,000 feet. As coal consists essentially of metamorphosed vegetable matter, fossil plants are very numerous in the carboniferous rocks, more than 1500 species of them having been named, a large proportion of which are ferns, tree, lycopods and large horse-tail like plants. The animals include insects, scorpions, amphibians, numerous corals, crinoids, molluscs, cephalopoda, sharks and other fishes.
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Carbuncle is a beautiful gem of a deep red colour (with a mixture of scarlet) . It was called by the Greeks anthrax and is found in the East Indies. When held up to the sun, it loses its deep tinge, and becomes of the colour of burning coal. The name belongs for the most part to ruby sapphire, though it has been also given to red spinel and garnet.
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Carminite is an arsenate mineral of a striking red colour formed in veins of iron and lead ore. Carminite was identified as a distinct mineral in 1850.
Carminite is a readily soluble compound of arsenic acid, oxygen, lead and iron.
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Carnallite is a light mineral found in marine evaporate deposits. It is a source of potassium compounds and magnesium. Carnallite has a bitter salty taste and easily absorbs water. It has the formulae KMgCl3ù6H2O and a relative hardness of 3.
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Carnelian is a clear red chalcedony, a semi-precious gemstone, consisting of quartz with iron impurities which give it a translucent red colour.
Carnelian is found mainly in Brazil, Japan and India.
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Carnotite is an ore of uranium and vandium. Found in sand, sandstones and around petrified trees. Probably formed as a deposition from meteoric waters. It is strongly radioactive and has the formulae K2(UO2)2(VO4)2ù 3H2O and a relative hardness of 1.
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Cassiterite is the principal ore of tin. It is widely distributed in small amounts but commercially available in only a few localities. It is frequently associated with wolframite. Native tin dioxide, it is found occurring in tetragonal crystals of reddish brown colour, and brilliant adamantine lustre; also massive, sometimes in compact forms with concentric fibrous structure resembling wood ('wood tin')It is also found as rolled pebbles in placer deposits ('stream tin') but is usually found in veins associated with quartz, in or near granitic rocks. It has the formulae SnO2 and a relative hardness of 7.
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Castor is a variety of the mineral petalite, from Elba.
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Cat's eye is a variety of quartz or chalcedony, exhibiting opalescent reflections from within, like the eye of a cat. The name is given to other gems affording similar effects, especially chrysoberyl.
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Cawk is an opaque, compact variety of barite, or heavy spar.
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Celestite (also known as celestine) is a natural sulphate of strontium, so named from its occasional delicate blue colour. It occurs crystallized, also in compact massive and fibrous forms. Celestite is often found disseminated through limestone or sandstone, or lining cavities in such rocks. It is associated with calcite, dolomite, gypsum, sulphur, fluorite and is also found as a gangue mineral in lead veins. It is an important source of strontium and is used to prepare nitrate of strontium for fireworks and tracer bullets, and in the refining of beet sugar. It has the formulae SrSO4 and a relative hardness of 4.
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Cerargyrite is native silver chloride, a mineral of a white to pale yellow or grey colour, darkening on exposure to the light. It may be cut by a knife, like lead or horn (hence it is also called horn silver).
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Cerite is a mineral of a brownish of cherry-red colour, commonly massive. It is a hydrous silicate of cerium and allied metals.
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Cerolite is a hydrous silicate of magnesium, allied to serpentine, occurring in wax like masses of a yellow or greenish colour.
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Ceruleite is a sky-blue coloured arsenate mineral similar in appearance and hardness to turquoise first discovered in the Emma Louisa gold mine in Huanaco, Chile and confirmed as a distinct mineral in 1900.
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Cerussite (lead carbonate) is an important and widely distributed supergene lead ore formed by the action of carbonated waters on galena in the upper zone of lead veins. It is often found associated with galena and sphalerite. It has the formulae PbCO3 and a relative hardness of 4.
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Ceylanite (pleonaste) is a dingy blue, or greyish black, variety of spinel.
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Chabasite is a mineral occurring in glassy rhombohedral crystals, varying in colour from white to yellow or red. It is essentially a hydrous silicate of alumina and lime.
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Chabazite is a complex hydrated calcium and sodium silicate mineral of secondary origin found lining cavities in volcanic and intrusive igneous rocks. It occurs as white to flesh-red crystals which vary from transparent to translucent and have a vitreous lustre. The crystals are rhombohedral. It has the formulae Ca(Al2Si4)O126H2O and a relative hardness of 5.
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Chalcanthite is native blue vitriol, a minor ore of copper found only in arid regions. It occurs near the surface in copper veins and is often deposited on iron from the water in copper mines. It is used in calico printing, insecticides and for industrial purposes. It has the formulae CuSO45H2O and a relative hardness of 3.
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Chalcedony is a cryptocrystalline, translucent variant of quartz comprised of silica, having usually a whitish colour, and a lustre nearly like wax.
Chalcedony was named after Chalkedon, near Istanbul. It was traditionally used for decorative objects and amulets. It has a relative hardness of 7. When chalcedony is variegated with spots or figures, or arranged in differently coloured layers, it is called agate; and if by reason of the thickness, colour, and arrangement of the layers it is suitable for being carved into cameos, it is called onyx. Chrysoprase is green chalcedony; carnelian, a flesh red, and sard, a brownish red variety.
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Chalcocite is one of the most important copper ore minerals. It is native copper Sulphide and is also called copper glance, and vitreous copper. It is a mineral of a black colour and metallic lustre occurring primarily in enriched zones of sulphide deposits. It has the formulae Cu2S and a relative hardness of 3.
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Chalcopyrite, Copper pyrites, or yellow copper ore, is the most widely occurring copper mineral and one of the most important ore sources of that metal, also containing iron, and sulphur. It occurs massive and in tetragonal crystals of a bright brass yellow colour as an original constituent of igneous rocks, in pegmatic dikes, and in contact with metamorphic deposits. May carry gold or silver and become an ore of those metals. It has the formulae CuFeS2 and a relative hardness of 4.
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Chalcosine (chalcosite) is both a primary and a secondary mineral and an important copper ore. It is an opaque, dark grey mineral with a metallic lustre that was discovered in the 16th century. The copper, which makes up as much as 80 percent of the weight of the mineral may be easily extracted by smelting.
Chalcosine can be difficult to identify as it frequently occurs as a pseudomorph of other minerals - it replaces the other species atom by atom but leaves their original crystal shapes intact, resulting in a mineral that has the outward shape of the original mineral, but the chemical composition and structure of
chalcosine.
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Chalk is a pure soft limestone, opaque white, and usually formed by the accumulation of the shells of foraminifera together with those of larger marine organisms. Chalk is found in large quantities in land masses which were at one time covered by the sea. Chalk is composed of between 50 and 98 percent calcium carbonate and various of minerals including clay, hematite, mica, quartz and pyrite. Chalk is important in industry and is used in the manufacture of rubber goods, paint, putty, polishing powders, cement, as well as the familiar writing implements beloved by school teachers.
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Chalybite, spathic iron ore or spathose iron is an iron carbonate, yellowish-grey to brown in colour. It is a common gangue mineral in metalliferous veins found in the coal measures of England, the Lias beds of Yorkshire, in the USA and in Germany and other places, providing an important ore of iron.
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Chamosite is a usually dark green in colour mineral of the chlorite group named after the place where it was first discovered - Chamoson in the Swiss Alps.
Chamosite occurs mainly in compact, massive aggregates and is thought to have two different crystal forms. The accredited species has a monoclinic crystal, but the variant species, orthochamosite is orthorhombic.
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Charoite is a rare mineral resembling purple marble, found only along the Chary river in Russia, used as an ornamental stone and as a gem stone. Charoite has a relative hardness of 5.
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Chatoyant refers to a hard stone, such as the cat's-eye, which presents on a polished surface, and in the interior, an undulating or wary light.
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Chert (hornstone) is a mineral very similar to flint, but coarser and less uniform in colour. It is found principally in association with limestones, especially in the carboniferous limestone of Ireland where beds of it are found several hundred feet thick. It appears to have resulted from the solution and redeposition of the silica of certain kinds of fossils, particularly of sponges, with the pointed spicules of which it is often filled. Radiolarian chert is a streaky, dark-grey, brown or reddish rock which under the microscope is seen to consist of innumerable shells of Radiolaria firmly united together by a siliceous cementing material.
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Chessy copper or chessylite is the name given to the mineral azurite, found in fine crystallization at Chessy, near Lyons.
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Chiastolite (macle) is a variety of andalusite. The tessellated appearance of a cross section when it is sliced, is due to the symmetrical arrangement of impurities in the crystal.
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Childrentite is a brown or yellow coloured mineral with a vitreous lustre named after John Children, the English doctor and naturalist who helped to identify it, childrentite being confirmed as a distinct mineral species in 1823.
Childrentite is similar to eosphorite, but contains more iron than manganese.
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China clay is a fine, white amorphous powder formed as a result of the decomposition of granite.
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Chlorite is a mineral group whose members usually exhibit a characteristic green colour, opaque, usually friable or easily pulverized, composed of little spangles, scales, prisms, or shining small grains, and consisting of silica, alumina, magnesia, and protoxide of iron. Chlorite is distinguished from muscovite and green phlogopite by a lack of elasticity. It has a relative hardness of 3. There are four subspecies - chlorite earth, common chlorite, chlorite slate, and foliated chlorite.
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Chlorite slate is a schistose or slatey rock consisting of alumina, iron, and magnesia.
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Chloropal is a massive mineral, greenish in colour, and opal-like in appearance. It is essentially a hydrous silicate of iron.
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Chlorophane is a variety of fluor spar, which, when heated, gives a beautiful emerald green light.
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A chondrite is a meteoric stone characterized by the presence of chondrules.
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Chondrodite is a common metamorphic mineral, a fluosilicate of magnesia and iron, yellow to red in colour, often occurring in granular form in a crystalline limestone in dolomitic marbles. It has the formulae (Mg,Fe)3 (SiO4)(OH,F)2 and a relative hardness of 7.
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Chondrules are peculiar rounded granules of some mineral, usually enstatite or chrysolite, found imbedded more or less abundantly in the mass of many meteoric stones, which are hence called chondrites.
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Chromite is a black sub-metallic mineral consisting of oxide of chromium and iron. It is slightly magnetic and the only ore of chromium. A common constituent of peridotite rocks and the serpentines derived from them. Also associated with corundum. One of the first minerals to separate from a cooling magma. Chromium is widely used in metal plating and in stainless steel. It has the formulae FeCr2O4 and a relative hardness of 6.
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Chrysoberyl is a mineral occurring in granite rocks, pegmatites, and in mica schists. It is frequently found in river sand and gravels in round pieces about the size of a pea, but also crystallized in eight-sided prisms.. It serves as a gem stone: cymophane, oriental chrysolite, alexandrite and 'cats eye' which can be of great value. It has the formulae BeAl2O4 and a relative hardness of 9. *Chrysocolla
Chrysocolla is a hydrous silicate of copper, occurring massive, of a blue or greenish blue colour. It is a minor ore of copper and a mineral of secondary origin, occurring in the oxidised zones of copper veins. It is associated with malachite, azurite, cuprite, native copper. It is named from two Greek words meaning 'gold' and 'glue'.
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Chrysolite is a mineral, composed of silica, magnesia, and iron, of a yellow to green colour. It is harder than glass, but less hard than quartz; often transparent, sometimes only translucent. Very fine specimens are found in Egypt and Brazil, but it is not of high repute as a jeweller's stone. It is common in certain volcanic rocks and is sometimes used as a gem. The name was also early used for yellow varieties of tourmaline and topaz.
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Chrysoprase is a green variety of chalcedony, coloured by nickel. When heated or exposed to sunlight the mineral often becomes paler, the colour being restored after exposure to moisture. It is a brittle mineral and is inclined to crack in cutting or setting. It is often extremely beautiful, so that it is much esteemed in jewelry. It is translucent, or sometimes semi-transparent, and of a hardness a little inferior to that of flint.
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Chrysostom is a gem stone of beryllium aluminate.
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Cimolite (cimolian earth) is a soft, earthy, clayey mineral, of whitish or greyish colour named from Cimolos or Argentiera, one of the Cyclades, where it is still to be found. It is a fine powder, and effervesces with acids. In classical times it was used as a detergent, as a soap for cleaning delicate fabrics, and by the bath-keepers.
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Cinnabar (vermilion) is a red crystalline form of mercuric sulphide. It has the formulae HgS and a relative hardness of 3. It often has a bright red colour. The only important source of mercury and it's found in few localities. Occurs as vein fillings near recent volcanic rocks and hot springs. Used in scientific equipment, in drugs, and with tin in silvering mirrors. Many other uses.
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Cinnamon stone is a variety of garnet, of a cinnamon or hyacinth red colour, sometimes used in jewellery.
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Cipolin is a whitish marble, from Rome, containing pale greenish zones. It consists of calcium carbonate, with zones and cloudings of talc.
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Clastic rock refers to a sedimentary rock comprised of fragments of pre-existing rocks that have been transported and deposited, for example sand.
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Clay is the name of various earths, which consist of hydrated silicate of aluminium, with small proportions of the silicates of iron, calcium, magnesium, potassium, and sodium. All the varieties are characterized by being firmly coherent, weighty, compact, and hard when dry, but plastic when moist and comprising very fine-grained materials (less than 0.004 mm in diameter), smooth to touch, not readily diffusible in water, but when mixed not readily subsiding in it. Their tenacity and ductility when moist and their hardness when dry has made them from the earliest times the materials of bricks, tiles, pottery, etc.
Of the chief varieties porcelain-clay, kaolin, or china-clay, a white clay with occasional gray and yellow tones, is the purest. Potter's-clay and pipe-clay, which are similar but less pure, are generally of a yellowish or grayish colour, from the presence of iron. Fire-clay is a very refractory variety, always found lying immediately below the coal; it is used for making fire-bricks, crucibles, etc. Loam is the same substance mixed with sand, oxide of iron, and various other foreign ingredients. The boles, which are of a red or yellow colour from the presence of oxide of iron, are distinguished by their conchoidal fracture. The ochres are similar to the boles, containing only more oxide of iron. Other varieties are f'uller's-earth, Tripoli, and boulder-clay, the last a hard clay of a dark-brown colour, with rounded masses of rock of all sizes embedded in it, the result of glacial action.
The distinctive property of clays as ingredients of the soil is their power of absorbing ammonia and other gases and vapours generated on fertile and manured lands; indeed no soil will long remain fertile unless it has a fair proportion of clay in its composition. The best wheats both in Britain and the European continent are grown on calcareous clays.
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In geology, clay-slate is a rock consisting of clay which has been hardened and otherwise changed, for the most part extremely fissile and often affording good roofing-slate. In colour it varies from greenish or bluish grey to lead colour. The cleavage is independent of the stratification. It rarely lies parallel to the bedding, generally crossing the strata at all angles.
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Cleavage is the structural lines along which a mineral will break up when it is subjected to pressure, such as being struck a sharp blow. The regular structure of most crystallized bodies becomes manifest as soon as they are broken. Each fragment presents the form of a small polyhedron, and the very dust appears under the microscope an assemblage of minute solids, regularly terminated. The directions in which such bodies thus break up are called their planes of cleavage; and the cleavage is called basal, cubic, diagonal, or lateral (or peritomous), according as it is parallel to the base of a crystal, to the faces of a cube, to a diagonal plane, or to the lateral planes. In certain rocks again there is a tendency to split along planes which may coincide with the original plane of stratification, but which more frequently cross it at an angle. This tendency is the consequence of the readjustment by pressure and heat of the components of rocks, which is one of the phases of metamorphism.
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Cleavelandite, named after professor Parker Cleaveland, is a variety of albite, white and lamellar in structure.
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Cleveite is a uranium-containing mineral, of interest owing to the fact that when heated with dilute sulphuric acid it liberates considerable quantities of occluded helium. It was this property which first led to the discovery of the element helium.
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Clinochlore is a mineral of the chlorite group and occurs as colourless, white, yellow or green monoclinic crystals found in metamorphic rocks, particularly in schist.
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Clinozoisite is a hydrous silicate of calcium and aluminium mineral found mainly in regional metamorphic rocks and in smaller contact zones of altered limestone. It occurs in varied external appearances, prismatic, needle-like crystals, shapeless, granular or fibrous aggregates. It has the formulae Ca2Al3Si3O12(OH) and a relative hardness of 7.
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Coal is a solid, opaque, inflammable substance, mainly consisting of carbon, found in the earth, largely employed as fuel, and formed from vast masses of vegetable matter deposited through the luxuriant growth of plants in former epochs of the earth's history. In the varieties of coal in common use the combined effects of pressure, heat, and chemical action upon the substance have left few traces of its vegetable origin; but in the sandstones, clays, and shales accompanying the coal, the plants to which it principally owes its origin are presented in a fossil state in great profusion, and frequently with their structure so distinctly retained, although replaced by mineral substances, as to enable the microscopist to determine their botanical affinities with existing species.
The sigillaria and stigmaria, the lepidodendron, the calamite, and tree-ferns are amongst the commoner forms of vegetable life in the rocks of the coal formation. Trees of considerable magnitude have also been brought to light, having a recognizable relation to the modern araucaria. The animal remains found in the coal-measures indicate that some of the rocks have been deposited in fresh water, probably in lakes, whilst others are obviously of estuarine origin, or have been deposited at the mouths of rivers alternately occupied by fresh and salt-water. The great system of strata in which coal is chiefly found is known as the Carboniferous. There are many varieties of coal, varying considerably in their composition, as anthracite, nearly pure carbon, and burning with little flame, much used for furnaces and malt kilns; bituminous (popularly so called) or 'household coal'; and cannel or 'gas-coal,' which burns readily like a candle, and was much used in gas-making. The terms semi-anthracitic, semi-bituminous, caking-coal, splint coal, etc, are also applied according to peculiarities. All varieties agree in containing from. 60 to over 90 per cent of carbon, the other elements being chiefly oxygen and hydrogen, and frequently a small portion of nitrogen.
Lignite or brown coal may contain only 50 per cent of carbon or less. For manufacturing purposes coals are generally considered to consist of two parts, the volatile or bituminous portion, which yields the gas used for lighting, and the substance comparatively fixed, usually known as coke, which is obtained by heating the coal in ovens or other close arrangements, and thus removing the volatile or smoke-yielding matter, while the full heating power of the coal still remains in the coke. Coal was the most valuable of all the minerals which contributed to the former wealth of Great Britain, and it has been mined there for many centuries. The first charter giving liberty to the town of Newcastle-upon-Tyne to dig coal was granted by Henry III in 1239; in Scotland a charter was granted to the abbot and convent of Dunfermline in 1291 for the same purpose. The working of coal gradually but slowly increased, until towards the end of the 18th century, when the development of the steam-engine by James Watt enormously increased the use of coal, and made it the basis of Great Britain's industrial importance. Towards the end of the 20th century political disputes between the miners and the government led to the closure of most of Britain's coal mines, with coal being imported instead.
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Coal brass is a name for iron pyrites found in coal-measures, so named from its brassy appearance.
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Coal-measures are the upper division of the carboniferous system, consisting of beds of sandstone, shale, etc, between which are coal-seams.
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Cobaltite (cobalt glance) is an ore of cobalt consisting of a cobalt arsenosulphide of the formulae CoAsS and has a relative hardness of 6. It is usually found in high temperature deposits, disseminated in metamorphic rocks, or in vein deposits with other cobalt and nickel minerals.
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A cobble is a class of rock between 64 and 256 mm in diameter.
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Coccolite is a granular variety of pyroxene, green or white in colour.
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Coelestine is a mineral used in pyrotechnics and a s a source of strontium. Occasionally it is cut and used as a gem stone. It has a relative hardness of 3.5.
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Colemanite, named after W.T. Coleman of San Francisco, is a hydrous borate of lime occurring in transparent colourless or white crystals, also massive, in Southern California. It is a major source of borax and has a relative hardness of 5. It occurs in high temperature hydrothermal veins or disseminated in metamorphic rocks associated with other cobalt and nickel sulphides/arsenides.
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Cologne earth is an earth of a deep brown colour, containing more vegetable than mineral matter. The name is also given to an earthy variety of lignite, or brown coal.
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Colophonite is a coarsely granular variety of garnet.
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Coloradoite is mercury telluride, an iron-black metallic mineral, found in Colorado.
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Columbite is a mineral of a black colour, sub-metallic lustre, and high specific gravity. It is a niobate (or columbate) of iron and manganese, containing tantalate of iron, was first found in New England and is the main ore of niobium and tantalum. It shows a bluish iridescent fracture surface and is used in metallurgy to create heat-resistant alloys and in the rust proofing of stainless steel. It has the formulae (Fe,Mn)(Nb, Ta)2O6 and a relative hardness of 6.
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Concretion refers to an accumulation of mineral matter when mineral particles become cemented together into an orderly, rounded form.
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Condurrite is a variety of the mineral domeykite, or copper arsenide, from the Condurra mine in Cornwall, England.
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In geolology, the term comformable refers to lying in parallel or nearly parallel planes, and having the same dip and changes of dip. Conformable is said of strata, the opposite term being unconformable.
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In geology, a conglomerate (popularly known as pudding-stone) is a coarse-grained sedimentary rock composed of rounded fragments embedded in a matrix of a cementing material such as silica.
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Conichalcite is a mineral of the adelite group, often brilliant green in colour, it is a secondary mineral that forms in the oxidation zones of copper ore bodies. It is often found as an encrustation on rocks composed mainly of limonite, where it is associated with adamite, azurite, bayldonite, linarite, malachite, olivenite and smithsonite. Conichalcite was confirmed as a distinct species of mineral in 1849 and is sometimes used as an ore of copper.
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Conite is a magnesian variety of dolomite.
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Connellite is a blue coloured mineral confirmed as a distinct species in 1850 and named after Arthur Connell, professor of geology at St Andrew's University, Scotland. Connellite is a secondary mineral, a hydrated copper chloride sulphate hydroxide, formed in the oxidation zones of copper deposits. Despite being a rare mineral, it is sometimes used as an ore of copper.
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Contact metamorphism refers to metamorphism resulting from the intrusion of magma which takes place at or near the contact point with the molten rock.
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Copper is one of the most anciently known metals, deriving its name from Cyprus, large supplies having in Greek and Roman times come from that island. It is a metal of a pale red colour tinged with yellow; chemical symbol Cu, atomic weight 63.6. Next to gold, silver, and platinum it is the most ductile and malleable of metals; it is more elastic than any metal except steel, and the most sonorous of all except aluminium. Its conducting power for heat and electricity is inferior only to that of silver. It has a distinct odour and a nauseous metallic taste. It is not affected by water, but tarnishes on exposure to the air, and becomes covered with a green carbonate.
Copper occurs native in branched pieces, dendritic, in thin plates, and rarely in regular crystals, in the primitive and older secondary rocks. Blocks of native copper have sometimes been found weighing many tons. Its ores are numerous and abundant. Of these several contain sulphur and iron or other metal, such as copper glance or vitreous copper (Cua S); gray copper or Fahlerz, one of the most abundant and important ores; and copper pyrites or yellow copper ore (CuFeSg), another abundant ore. The red oxide of copper forms crystals of a fine red colour, and is used for colouring glass.
There are two native carbonates, the blue and the green, the latter being the beautiful mineral malachite, the former also known as blue malachite. Blue vitriol is a sulphate, and is used for dyeing and preparing pigments, as are various other copper compounds. Verdigris is an acetate. The arsenite of copper is the pigment Scheele's green. Schweinfurth green is another copper pigment. All the compounds of copper are poisonous.
Copper is found in most European countries, in Australia and Japan, in Africa and in North and South America (especially in the vicinity of Lake Superior). In Britain the mines of Cornwall have yielded little copper since the end of the 19th century.
Copper is extracted from its ores either by the dry or the wet process. For the former, what is known as the Welsh process is most common in Great Britain. It consists in alternately roasting the ore, and then smelting it in a furnace with a suitable slag, until impure or blister copper is obtained. Before this stage is reached a metallic compound of copper, sulphur, and iron has been produced, technically known as matt, regulus, or coarse metal, and subsequently a tolerably pure sulphide of copper called fine metal. The blister copper is refined by burning off the sulphur, arsenic, and other volatile impurities, and by melting it along with wood charcoal and stirring it with a wooden pole. The quality is then tested, and, if found satisfactory, the copper is cast into ingots.
In extracting the metal from pyrites by the wet process, the ore is first roasted to get rid of the larger proportion of sulphur, then the calcined residue still containing sulphur is mixed with common salt, ground and heated in ovens. The copper is thus converted into chloride, part of which volatilizes, but is condensed, along with arsenic and other substances, by passage through flues and water-condensers. After some hours the calcined mixture is raked out of the ovens, cooled, and transferred to tanks, where it is exhausted by successive treatment with water. The solution, containing chloride of copper, sulphate and chloride of sodium, and iron salts, is next heated along with scrap-iron. Copper precipitates in the form of a ruddy, lustrous, tolerably compact mass, with a crystalline appearance, and mixed with metallic-iron and oxide. The larger pieces of iron are picked out, the precipitate washed and drained, and then rendered compact by heating in a furnace. A slag containing the oxide of iron forms, and the copper, when judged sufficiently pure, is run into moulds.
The crude metal is now usually refined by an electrolytic process, the crude metal serving as anode and a strip of pure copper as cathode. Many alloys of copper, especially those containing tin and zinc, are of much importance, eg, brass, an alloy of copper and zinc; bronze, an alloy of copper with about 8 or 10 per cent of tin; bell-metal, composed of eighty parts of copper and twenty of tin.
Copper is applied to a great many useful purposes. In sheets it is used for the constructing of boilers and stills of a large size, etc; and pipes of various sorts, as well as electircla circuits, wire, lightning-rods, etc., are made of it. It is also used in electrotyping and engraving, for various household utensils and fittings; but its use for household utensils is by no means free from danger on account of the formation of verdigris by the action of acids.
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Copper barilla is native copper in granular form mixed with sand. It is an ore brought from Bolivia.
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Copper glance is a copper ore of a lead or iron-grey colour. It consists of 81 percent copper and 19 percent sulphur, and abounds in Cornwall and many European countries.
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Copper pyrites or yellow copper is an ore, a double sulphide of copper and iron composed in equal parts of copper, sulphur, and iron. It occurs mostly in primary and metamorphic rocks, and is the chief copper ore of England.
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Copper-nickel or Kupfernickel is an ore of nickel, an alloy of nickel and arsenic, containing about 60 percent of the former and 40 percent of the latter, of a copper colour it is found in the mines of Westphalia.
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Copperas is a sulphate of iron or green vitriol, a salt of a peculiar astringent taste and of a fine green colour. When exposed to the air it assumes a brownish hue. It is much used in dyeing black and in making ink, and in medicine as a tonic. The copperas of commerce is usually made by the decomposition of iron pyrites.
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In geology, the coral rag is the highest member of the middle Oolitic series - a limestone containing many petrified corals, occurring in some parts of England.
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Corallite is a mineral substance or petrifaction, in the form of coral.
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Cordierite is found as an accessory mineral in granite, gneiss, schists, and in contact metamorphic zones. Transparent specimens of good colour have been used as a gem stone. It has the formulae Mg2Al4Si5O18 and a relative hardness of 8.
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Cork fossil is a variety of amianthus which is very light, like cork.
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Cornbrash is a local name in England for a rubbly limestone, forming a soil extensively cultivated in Wiltshire for the growth of corn. The term is used by geologists to indicate the strata which yield the soil, the highest member of the lower Oolite.
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Cornetite is a rare, brittle, secondary mineral with a chemical composition similar to turquoise. Cornetite is formed in the weathered oxidation zones of copper sulphide ore bodies and is found in association with brochantite, chrysocolla, liberthenite, limonite, malachite and pseudomalachite. Cornetite was first discovered in 1912 and was confirmed as a distinct mineral in 1917, subsequently being named after the Belgian geologist Jules Cornet. Cornetite is a naturally occurring hydrous phosphate of copper, as is also turquoise.
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Cornish diamond is a variety of quartz found in Cornwall and employed even in the 16th century for personal ornaments. This variety being now scarce, ordinary rock-crystal is often used instead.
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Corundum is a form of aluminium oxide common as an accessory mineral in metamorphic rocks and as an original constituent of certain igneous rocks. Pure corundum is colourless, but colour differences due to the presence of other elements give rise to several varieties of gem, notably, ruby and sapphire. The deep red ruby (corundum tainted with chromium) is one of the most valuable gems, second only to emerald and diamond. Sapphire is corundum tainted with titanium.
Corundum has the formulae Al2O3 and a relative hardness of 9.
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Covellite, named after its discoverer, Covelli, is an indigo-blue material found in most copper deposits, usually as a coating in the zone of sulphide enrichment. It has the formulae CuS and a relative hardness of 2.
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In geology, crag is a local name in England for shelly deposits in Norfolk and Suffolk, usually of gravel and sand, of the older pliocene period, subdivided into three members: the Upper or Mammaliferous Crag, the Red Crag, and the Lower or Coralline Crag.
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In geology, crag and tail or Craig and tail is a name applied to a hill formation common in Britain, in which a bold and precipitous front is presented to the west or north-west, while the opposite side is formed of a sloping declivity. The rock on which Edinburgh Castle stands, with its 'tail' gradually sloping down to Holyrood, presents a fine example. This phenomenon is due probably to the currents of the 'drift' or glacial epoch.
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The Cretaceous was the eleventh geological period, 95,000,000 years ago, following the Jurassic and preceding the Eocene. The first marsupials evolved during this period. The cretaceous forms the upper strata of the Secondary series, immediately below the Tertiary series, and superincumbent on the Oolite system. This group is common to Europe, and also to a part of Asia. It consists of chalk resting upon arenaceous and argillaceous deposits, which are also regarded as part of the system. It has been divided into two parts: the Upper, consisting entirely of chalk or marl, and subdivided into the upper or soft chalk, containing many flint and chert nodules; the lower or harder chalk, with fewer flints; and the chalk marl: and the Lower, consisting of sands and clay, and subdivided into the upper greensand; gault, a bluish tenacious clay; and the lower greensand. Palaeontologists have suggested another division founded on the fossil remains found in the system, in accordance with which the upper greensand and gault are transferred to the upper series, and the lower greensand and Wealden beds and Hastings sands constitute the lower.
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Cristobalite is a polymorph of trigonal quartz present in many siliceous volcanic rocks as a lining in cavities. Upon heating to 1470 C it becomes nearly transparent. On cooling it assumes its initial white translucent appearance. It has the formulae SiO2 and a relative hardness of 7. Cristobalite was confirmed as a distinct species of mineral in 1887 and named after the place where it was discovered - Cerro San Cristobal in Mexico.
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Crocidolite is a mineral occurring in silky fibres of a lavender blue colour. It is related to hornblende and is essentially a silicate of iron and soda. A silicified form, in which the fibres penetrating quartz are changed to oxide of iron, is the yellow brown tiger's-eye of the jewellers.
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Crocoite is a rare mineral found in the oxidized zones of lead deposits where lead veins have traversed rocks containing chromite. Not abundant enough to be of commercial value although it does contain chromium. It's name is Greek and means 'saffron', an allusion to its colour. It has the formulae PbCrO4 and a relative hardness of 3.
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Cronstedtite, named after the Swedish mineralogist Cronstedt, is a mineral consisting principally of silicate of iron, and crystallizing in hexagonal prisms with a perfect basal cleavage.
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Cryolite is the fluoride of sodium and aluminium, it is found in Greenland in pale greyish-white or yellowish-brown cleavable masses often enclosing brown siderite and grey galena. It always occurs in pegmatites where it's probably a precipitate from fluoride rich solutions. It has been used as a source of aluminium, and is used in the manufacture of sodium salts, certain kinds of high quality glass and hard porcelain, and as a flux for cleaning metal surfaces. It has the formulae Na3AlF and a relative hardness of 3 and has a vitreous lustre.
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In mineralogy, a crystal is any body which, by the mutual attraction of its particles, has assumed the form of some one of the regular geometric solids, being bounded by a certain number of plane surfaces. The chemist procures crystals either by fusing the bodies by heat and then allowing them gradually to cool, or by dissolving them in a fluid and then abstracting the fluid by slow evaporation. The method of describing and classifying crystals now universally adopted is based upon certain imaginary lines drawn through the crystal, and called its axes. The classes are as follow:
1st, The monometric, regular, or cubic system in which the axes are equal and at right angles to one another;
2nd, The square prismatic or dimetric system in which the axes are at right angles to each other, and while two are equal, the third is longer or shorter;
3rd, The right prismatic, rhombic, or trimetric system in which the axes are at right angles to each other, but all are of different lengths;
4th, The hexagonal or rhomhohedral system which has four axes, three in one plane inclined to each other at 60 degrees, the fourth perpendicular to this plane;
5th, The monoclinic or oblique system in which two axes are at right angles and the third is inclined to their plane;
6th, The diclinic or doubly oblique system in which two axes are at right angles, the third oblique to both;
7th, The triclinic system in which the three axes are inclined to each other at any angle other than a right angle.
A crystal consists of three parts. 1st, Plane surfaces, called faces, which are said to be similar when they are equal to one another and similarly situated; dissimilar, when they are unequal or have a different position. 2nd, Edges, formed by the meeting of two faces. They are said to be similar when formed by similar faces; dissimilar, by dissimilar faces. Equal edges are formed when the faces are inclined at the same angle to one another; unequal, when they are inclined at different angles. 3rd, Solid angles, formed by the meeting of three or more faces; and in this case also there are similar and dissimilar, equal and unequal solid angles, according as they are formed by similar or dissimilar faces, and equal or unequal angled edges. The angles of crystals are measured by an instrument called the goniometer.
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Crystal symmetry refers to the repetitive pattern of crystal faces caused by the orderly internal arrangements of atoms within a mineral.
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Cubic Nitre (also known as sodium nitrate, Chili Saltpetre) is a mineral found mainly in the Tarapaca district of Chile, where it occurs for the most part mixed with other salts, sand, and clay. It crystallizes in obtuse-angled rhombohedra, not in cubes, and is used in considerable quantities both as a dressing for grass and mixed in artificial manures. It has also been used as a source of nitric acid, and after double decomposition with chloride of potassium haa been employed in the manufacture of gunpowder.
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Culm is a name given to mineral coal that is not bituminous especially when it is found in small masses or dust. The term culm is also applied to a kind of impure anthracite coal.
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Cuprite is the red oxide of copper and an important ore of copper. It is found in the upper oxidized portions of copper veins and is commonly found in isometric crystal forms, and also massive. It has the formulae Cu2O and a relative hardness of 4.
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Cyanite or kyanite is an accessory mineral of the garnet family found both massive and in regular crystals in gneiss and mica schist. It often found with garnet and corundum. It is used in the production of refractory porcelains. It has the formulae Al2SiO5 and a relative hardness of 7. Its prevailing colour is blue but of varying shades.
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Cyanosite is native sulphate of copper.
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Abbreviations
Rocks & Minerals
