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Eclogite is a rock which consists of pale-green augite, pale-green hornblende, pink garnet with sometimes also quartz, feldspar, kyanite, bronzite, iron ores and rutile. Such rocks occur in regions of xrystalline schists, as the Alps, and are believed to be of intrusive origin in some cases.
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Elaterite is a natural bitumen, soft, brown and elastic found in the lead mines of Castleton in Derbyshire and in Edinburgh.
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Emerald is a green precious stone variety of the mineral beryl. While pure beryl is colourless, the green of the emerald comes from various impurities in the stone. Brazilian emeralds usually contain calcite or pyrite, South African and Russian emeralds usually contain mica.
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Emery is an impure fine-grained form of corundum (aluminium oxide) in conjunction with iron oxides and spinel, with the formulae Al2O3 employed widely as an abrasive. Typically emery consists of 60 percent corundum and 40 percent iron oxide in the form of magnetite.
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Enargite is a relatively rare mineral found in vein and replacement deposits associated with pyrite, sphalerite, bornite, galena, chalcocite. It is used as an ore of copper. It has the formulae Cu3AsS4 and a relative hardness of 4.
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Enstatite is a common and widespread mineral with a relative hardness of six. It is found in mafic plutonic and volcanic rocks and often in both metallic and stony meteorites. It is a silicate of magnesium and iron and has the formulae Mg2Si2O6. Enstatite has various uses depending upon the quality of its crystals, and is used as a gemstone and for lining ovens, due to its very high melting point.
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The Eocene System is the oldest of the four geological systems into which the Tertiary era is divided.
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Epidote is a common mineral found in regional and metamorphic rocks of mafic composition and as a product of alteration of other minerals. It is sometimes used as a gemstone. It has the formulae Ca2(Al,Fe)3Si3O12(OH) and a relative hardness of 7.
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Epsomite (popularly known as 'Epsom Salts') is a mineral named after Epsom in Surrey, England where it is found occurring around mineral springs. Although large crystals of epsomite have been found, it is most commonly found as an encrustation or massive aggregate on the surface of other rocks and minerals as a white fibrous mass of acicular micro-crystals.
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Erratics are rocks transported by the action of ice during the Quaternary Glacial Period, often for considerable distances. They help in determining the extent of the ice-sheets and the direction of their movement.
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Erythrite is a secondary mineral which often shows a vivid colour and occurs in thin crusts. It is an important indicator of cobalt mineral deposits, being formed through the oxidation of cobaltite in veins and has the formulae Co3(AsO4)2ù8H2O and a relative hardness of 3.
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Ettringite is a mineral first found at Ettringen in Germany, and named after the place of its discovery. It is a hydrous sulphate of calcium and aluminium which forms small but beautifully formed hexagonal prism crystals, generally yellow in colour.
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Euclase is a variety of beryl and has the formulae BeAlSiO4(OH) and a relative hardness of 8.
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Eudialyte is a rare and complex silicate mineral easily soluble in acids.
Eudialyte crystals are trigonal and appear in prismatic or table-top shapes, often pink in colour they may also be yellowish-brown. Eudialyte was confirmed as a distinct mineral in 1819, but its chemical formula is still in doubt.
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Eurite is an acid, igneous rock of the granite group, which consists of quartz and feldspar with muscovite or garnet as accessory minerals, and is mostly found as dykes and veins traversing granite and crystalline schists.
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In geology, extravasation describes the issue of lava and other volcanic products from the earth.
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Abbreviations
Rocks & Minerals
