COMPOUNDS OF CALCIUM. 213 



mammillary with a compact fibrous structure. 

 Small crystals are occasionally transparent 

 and colorless, but the usual color is green, 

 often yellowish green, bluish green, and gray- 

 ish green ; sometimes yellow, blue, reddish 

 or brownish. Coarse crystals nearly opaque. 



Lustre vitreous to subresinous. H. = 5. G-. 

 = 3-3*25. Brittle. Some varieties phospho- 

 resce when heated, and some become electric 

 by friction. 



* Composition. Ca ? O s P 2 + i (Cl 2 , F 2 ) = if without fluorine 

 Phosphorus pentoxide 40*92, lime 53*80, chlorine 6*82 = 100. 

 "When chlorine is present in place of fluorine it is called 

 c dor-apatite, and when the reverse, fluor-apatite. B.B. in- 

 fusible except on the edges. Dissolves slowly in nitric acid 

 without effervescence. Its constituents are contained iii 

 the bones and ligaments of animals, and the mineral has 

 probably been derived in many cases from animal fossils.* 



Massive apatite is often called Phosphorite ; and the pale 

 yellowish-green crystals, Asparagus stone. Osteolite is a 

 white earthy apatite. Eupyrchroite is a fibrous mammil- 

 lary variety from Crown Point, Essex County, N. Y. 



Fossil excrements, called coprolitcs, occur in stratified 

 rocks, and sometimes constitute extended beds ; and they 

 consist chiefly of calcium phosphate. Guano contains more 

 or less calcium phosphate along with hydrous phosphates 

 and some impurities. 



Diff. Distinguished from beryl by its inferior hardness, 

 it being easily scratched with a knife ; from calcite by dis- 

 solving in acids without effervescence ; from pyromorphite 

 by its difficult fusibility, and giving no metallic reaction 

 before the blowpipe. Phosphoric acid may be detected by 

 moistening it with sulphuric acid and igniting it B.B., 

 when it imparts a dirty green color to the flame. 



Obs. Apatite occurs in gneiss, mica schist, hornblende 

 schist, granular limestone. In microscopic crystals it is 

 sparingly present in almost all crystalline rocks, the ig- 

 neous as well as metamorphic. The best crystals in the 

 United States occur in granular limestone ; the crystals 

 from the limestone of St. Lawrence County, N. Y., are 



* Bones contain 25 per cent, of calcium phosphate, with some fluoride of calcium, 3 

 to 12 per cent, of calcium carbonate, some magnesium phosphate and sodium chloride, 

 besides 33 per cent, of animal matter. 



