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A fahlband is a stratum in crystalline rock, containing metallic sulphides.
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Fahlunite, named after Fahlun in Sweden, is a hydrated silica of alumina, resulting from the alteration of iolite.
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The faluns is a series of strata, of the Middle Tertiary period, of France, abounding in shells, and used by Sir Charles Lyell as the type of his Miocene subdivision.
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In geology, a famp is an indurated wavy calcareous shale found among limestone rocks.
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Farcilite was an old mineralogical term for a conglomerate.
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Fassaite, named after the Fassa valley in the Tyrol, is a variety of pyroxene.
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Faujasite, named after the French geologist Faujas de Saint-Fond is a silicate occurring in square octahedrons together with black augite in the mandelstein of the Kaiserstuhl in Baden.
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In geology, a fault is a dislocation caused by a slipping of rock masses along a plane of facture. The term also describes the dislocated structure resulting from such slipping. The surface along which the dislocated masses have moved is called the fault plane. When this plane is vertical, the fault is a vertical fault; when its inclination is such that the present relative position of the two masses could have been produced by the sliding down, along the fault plane, of the mass on its upper side, the fault is a normal, or gravity, fault. When the fault plane is so inclined that the mass on its upper side has moved up relatively, the fault is then called a reverse (or reversed), thrust, or over thrust, fault. If no vertical displacement has resulted, the fault is then called a horizontal fault. The linear extent of the dislocation measured on the fault plane and in the direction of movement is the displacement; the vertical displacement is the throw; the horizontal displacement is the heave. The direction of the line of intersection of the
fault plane with a horizontal plane is the trend of the fault. A fault is a strike fault when its trend coincides approximately with the strike of associated strata (i.e., the line of intersection of the plane of the strata with a horizontal plane) ; it is a dip fault when its trend is at right angles to the strike; an oblique fault when its trend is oblique to the strike. Oblique faults and dip faults are sometimes called cross faults. A series of closely associated parallel faults are sometimes called step
faults and sometimes distributive faults.
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Favosites (favosite) is a genus of fossil zoophyta resembling a honeycomb in appearance and common in the Silurian strata of Norway and Wales
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Fayalite, named after the island of Fayal, is a black, greenish, or brownish mineral of the chrysolite group. It is a silicate of iron.
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Feather alum or halotrichite, is a hydrous sulphate of alumina, resulting from volcanic action, and from the decomposition of iron pyrites.
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Feather ore is a sulphide of antimony and lead, sometimes found in capillary forms and like a cobweb, but also massive. It is a variety of Jamesonite.
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Feitsui is the Chinese name for a highly prized variety of pale green jade.
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Feldspar or felspar is a name given to a group of minerals, closely related in crystalline form, and all silicates of alumina with either potash, soda, lime, or, in one case, baryta. They occur in crystals and crystalline masses, vitreous in lustre, and breaking rather easily in two directions at right angles to each other, or nearly so. The colours are usually white or nearly white, flesh- red, bluish, or greenish. The group includes the monoclinic (orthoclastic) species orthoclase or common potash feldspar, and the rare hyalophane or baryta feldspar; also the triclinic species (called in general plagioclase) microcline, like orthoclase a potash feldspar; anorthite or lime feldspar; albite or soda feldspar; also intermediate between the last two species, labradorite, andesine, oligoclase, containing both lime and soda in varying amounts. The feldspars are essential constituents of nearly all crystalline rocks, as granite, gneiss, mica, slate, most kinds of basalt and trachyte, etc. The decomposition of feldspar has yielded a large part of
the clay of the soil, also the mineral kaolin, an essential material in the making of fine pottery. Common feldspar is itself largely used for the same purpose.
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Felsite is a fine grained rock, flint-like in fracture, consisting essentially of orthoclase feldspar with occasional grains of quartz.
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Fengite is a kind of marble or alabaster, formerly sometimes used for windows on account of its transparency.
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Ferberite is the chief ore of tungsten. It is a rare mineral found usually in pegmatite dikes and high- temperature quartz veins associated with granite. It has the formulae FeWO4 - MnWO4 and a relative hardness of 6.
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Fergusonite, named after Robert Ferguson, is a mineral of a brownish black colour, essentially a tantalo- niobate of yttrium, erbium, and cerium.
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Ferruginous refers to containing iron.
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Fichtelite is a white crystallized mineral resin from the Fichtelgebirge, Bavaria.
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Fiorite, so called from Fiora, in Ischia, is a variety of opal having a pearly lustre, occurring in the cavities of volcanic tufa, in smooth and shining globular and botryoidal masses.
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A fiveling is a compound or twin crystal consisting of five individuals.
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In geology, a flag is a hard, evenly stratified sandstone, which splits into layers suitable for flagstones.
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Flint is a massive compact variety of quartz comprised of fine grained silica. It is usually grey to brown or nearly black in colour and breaks with a conchoidal fracture and sharp edge. It is very hard, and strikes fire with steel.
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In geology, flocculation is the process by which small particles of fine soils and sediments aggregate into larger lumps.
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Flos-ferris is a variety of aragonite, occurring in delicate white coralloidal forms commonly in beds of iron ore.
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Flourite is a mineral usually found occurring in isometric cubic crystals or in massive formations. It is comprised of calcium fluoride with small amounts of yttrium and cerium. Flourite has a relative hardness of four and a low melting point. It is used as a flux in the smelting of metallic ores and as a semi-precious gem stone in jewellery.
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Flow banding refers to a structure sometimes found in volcanic rocks where alternating layers of rock have different mineral compositions.
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Fluocerine is a fluoride of cerium, occurring near Fahlun in Sweden.
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Fluorapatite is a common mineral consisting of a mixed phosphate and fluoride of calcium. It is a source of phosphorus and was formerly used to make phosphate fertiliser.
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Fluorine is a non-metallic element occurring naturally.
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Fluorite (calcium fluoride) or fluorspar is a mineral occurring in many different colours, found in veins where it's the main mineral or with metallic ores, especially lead and silver. It is common in dolomites and limestone and is associated with many different minerals. It is used chiefly as a flux in the making of steel, and also for enamelling, and in the preparation of hydrofluoric acid. It has the formulae CaF2 and a relative hardness of 4.
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In geology, the term fluvio-marine describes deposits formed by the joint action of a river and the sea, such as deposits at the mouths of rivers for example.
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The Flysch is a name given to the series of sandstones and schists overlying the true nummulitic formation in the Alps, and included in the Eocene Tertiary.
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In geology, the term foliation refers to the property, possessed by some crystalline rocks, of dividing into plates or slabs, which is due to the cleavage structure of one of the constituents, as mica or hornblende. It may sometimes include slatey structure or cleavage, though the latter is usually independent of any mineral constituent, and transverse to the bedding, it having been produced by pressure.
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A foralite is a tube-like marking, occurring in sandstone and other strata.
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Fowlerite, named after Dr. Samuel Fowler, is a variety of rhodonite, from Franklin Furnace, New Jersey, containing some zinc.
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Francolite is a variety of apatite from Wheal Franco in Devonshire.
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Franklinite is a mineral found in Franklin, New Jersey, and used as an ore of zinc and manganese. With minor exceptions, the mineral is confined to Franklin, New Jersey. It has the formulae (Zn,Mn,Fe)(Fe,Mn)2O4 and a relative hardness of 7. Franklinite exhibits increased magnetism when it is heated.
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Freibergite is a variety of terahedrite containing between 28 and 36 percent silver.
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French chalk is a variety of granular talc. It is used for drawing lines on cloth and is used by athletes and gymnasts to put on their hands to stop them slipping. In painting and decorating, French chalk is sometimes incorporated into paint as an extender to help keep the pigments in suspension.
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Friable refers to crumbles or is pulverized easily.
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In geology, the term fucoidal refers to rocks containing impressions of fossil fucoids or seaweeds such as fucoidal sandstone for example.
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Fulgurite is a term applied to rocks whose surface has been melted by the action of lightning, and on which the fused material has re-solidified as a kind of thin coat or varnish.
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Fuller's earth is a kind of clay or marl of highly absorbent properties, composed chemically of hydrous silicate of alumina. It derives its name from being used by fullers in the cleaning and felting of cloth.
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Abbreviations
Rocks & Minerals
