241 



MAGNESIUM. 



695. DOLOMITE. (Magnesian Limestone.) 



a. Massive specimens, from Sanderland. 



Note. These specimens were presented by Mr. Smith. Several of 

 them present an appearance like the vertebra of some animal. Dolo- 

 mite is a carbonate of calcium and magnesium, and is used in preparing 

 magnesia and magnesium salts. See Dana, Mineralogy, p. 682. 



696. MAQNESITE. (Native Carbonate of Magnesia.) 



a. Earthy, pure white, 

 t b. A fine specimen, presented by Messrs. Huskisson and 



Sons. 



Note. These specimens consist of almost pure carbonate of magnesium. 

 See Dana, Mineralogy, p. 686. 



697. BRUCITE. (Hydrate of Magnesia, Native Magnesia.) 



a. Foliated. 

 Note. This mineral usually contains traces of iron. 



698. DlALLAGE. 



a. Foliated, of a pale green tint. 



Note. Diallage is composed of the silicates of magnesium, calcium, and 

 iron. See Dana, Mineralogy, p. 215. 



699. MICA. (Biotite, Hexagonal Mica, Uniaxial Mica.) 



a. In shining laminae. 



Note. Biotite is chiefly a silicate of magnesium and aluminum, owing 

 its brownish tint to a portion of the aluminum being replaced by iron. 



700. ASBESTOS. 



a. Massive, probably from Cornwall. (Amphibole.) 



b. Fibrous, white. (Amianthus.) 



Note. Asbestos is a silicate of magnesium with varying proportions of 

 other elements. 



701. TALC. (Soapstone, Steatite, Potstone.) 



a. Massive. (French Chalk.) 



Note. This mineral is a bisilicate of magnesium with traces of iron 

 and aluminum. 



702. MEERSCHAUM. (Sepiolite.) 



a. Compact. 



N*ote. Meerschaum is an hydrated silicate of magnesium with traces 

 of aluminum. 



ZINC. 



703. CALAMINE. (Carbonate of Zinc, Smithsonite, Dry Bone.) 



a. Massive, from Cumberland. 



b. Prepared, six specimens. (Prepared Calamine.) 



Note. This mineral consists chiefly of the carbonate of zinc and iron 

 with traces of manganese and occasionally other elements. See Dana, 

 Mineralogy, p. 692. 



B 



