This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1850 edition. Excerpt: ... A GLOSSARY, Explaining the terms which generally occur in geological works. and the nature and composition of the principal mineral substances. Agate.--A siliceous or flinty mineral, which is considered a compound of many others, in which chalcedony mostly prevails over other ingredients, which consist of amethyst, quartz, cornelian, jasper, and opal. The varieties are ribbon agate, brecciated agate, fortification agate, from its resembling fortifications; mocha stone, moss agate. A labaster.--Compact gypsum, or sulphate of lime, which occurs extensively in the new red sandstone of England. There is another kind brought from Italy, which consists of a very pure carbonate of lime. Albite.--Also called Cleavelandite, a siliceous compact felspar, generally of a grey or greyish white colour, and consisting of silex 70'7, alumina 198, soda 90, lime 0-2, oxide of manganese (hi. Alkalies.--Mineral substances which serve as bases to form salts with acids; soda and potash are such alkalies. Alkaline Earths.--Earths which have the nature of alkalies, such as lime and magnesia. Alluvium.--Earth, sand, gravel, and other transported matter deposited by running water in valleys and estuaries. Alum.--A double salt, the sulphate of alumina and potash, the crystals of which contain nearly 50 per cent. of water. A lum Shale.--A shale from which alum is made. The slate clay of the lias affords a shale of this kind on the coast of Yorkshire, near Whitby. A lum Stone.--A mineral of a greyish white colour, and occasionally red. It occure both massive and crystalline. Analysis, by Vauquelin: --Alumina 43-92, silex 24-00, sulphuric acid 25-00, potash 3-08, water 4 00 Alumina.--The plastic principle of clay, consisting of aluminum 12, oxygen 8. Amalgam Native.--A..