688 APPENDIX 



with the finger nail (H = 2). Gypsum occurs in veins or beds; in 

 crystals, or compact, rocklike masses. The most important variety 

 is selenite, a crystalline gypsum with a perfect cleavage, thin leaves 

 of which may be split off and resemble those of mica. They differ 

 from the latter in their inelasticity and vertical cleavage. Alabaster 

 is a compact, fine-grained, usually translucent gypsum, used in making 

 ornaments and statuary. Satin spar is a fibrous gypsum which has 

 somewhat the appearance of satin. It is occasionally used in the 

 manufacture of cheap jewelry. Rock gypsum is compact and rock- 

 like. It is used for plaster of Paris. Gypsum is common in many 

 portions of North America, but is especially abundant in New 

 York, Iowa, Michigan, and Ohio. 



Fluorite (fluorspar, blue John), CaF 2 . — The color is commonly 

 blue or green, but is occasionally white or yellow. It is slightly harder 

 than calcite and can be scratched with a knife (H = 4). Its principal 

 use is as a flux in reducing iron, but it is used to some extent for orna- 

 mental purposes. It occurs in clear, cubical crystals, and in masses. 

 Fluorite is mined in Illinois and Kentucky. 



Apatite (asparagus stone, phosphate rock, calcium phosphate). — ■ 

 The color is usually green or reddish brown. It is harder than fluorite 

 and cannot easily be scratched with a knife (H = 5). After being 

 treated with sulphuric acid, it becomes a valuable fertilizer. It 

 is found in many parts of North America, but the most valuable de- 

 posits occur in Canada. 



Copper Minerals 



Chalcopyrite (copper pyrites), CuFeS 2 . — The color is a deeper yellow 

 than pyrite. Chalcopyrite can be easily scratched with a knife (H = 

 3.5) and this character alone easily distinguishes it from pyrite, but 

 not from pyrrhotite. The bluish tarnish of chalcopyrite is also dis- 

 tinctive. Since it is not attracted by a magnet, it is easily distinguish- 

 able from pyrrhotite. It is a valuable and widespread ore of copper 

 and is mined in many of the Western States. 



Malachite (green copper carbonate), (CuOH) 2 CO3. — The color 

 is bright green. The color, hardness, which is less than that of steel 

 (H = 3.5), and its effervescence with acids readily distinguish it from 

 other minerals. Its principal use in the United States is as an ore of 

 copper, although in Europe the compact varieties have long been much 

 sought after for vases, table tops, and mosaics. 



