306 DESCRIPTIONS OF MINERALS. 



makes the biscuit semi-transparent, but brittle and apt to 

 break with slight changes of heat. It forms a polishing 

 material for serpentine, alabaster and glass. "French 

 chalk" is used for removing grease-spots from cloth, as 

 well as for tracing on cloth. When ground up, soapstone 

 is employed for diminishing the friction of machinery. 



Pyrophyllite. — Agalmatolite, in part. 



Near -talc in crystallization, cleavage, its occurrence in 

 fine-grained massive forms, its greasy feel, its white to pale- 

 green colors, varying to yellowish, its feeble degree of hard- 

 ness (1-2). The folia are sometimes radiated. G. =2*75- 

 2-92. 



Composition. An aluminous bisilicate, instead of a mag- 

 nesian, for the most part of the formula, Al 9 Si 3 . The 

 Chesterfield, S. C, mineral afforded Genth, Silica 64*82, 

 alumina 24'4S, iron sesquioxide 0*96, magnesia 0*33, lime 

 0-55, water 5*25 — 100*39. B.13. whitens and fuses with dif- 

 ficulty on the edges. Gives a deep blue color with cobalt 

 solution. Yields water in the closed tube. Radiated varie- 

 ties exfoliate in fan-like forms. 



Obs. Compact pyrophyllite is the chief constituent of a 

 kind of slate or schist, which is used for slate pencils, and 

 hence is called ■pencil-stone. Occurs in the Urals ; at Wes- 

 tana in Sweden ; in Elfdalen, with cyanite ; foliated, in 

 North Carolina, in Cottonstone Mountain ; in South Caro- 

 lina, in Chesterfield District, with lazulite and cyanite ; 

 Georgia, in Lincoln Count} T , on Graves Mountain ; in Ar- 

 kansas, near Little Rock ; compact slaty in the Deep River 

 region, X. C, and at Carbonton, Moore County, N. C. 



Sepiolite. — Meerschaum of the Germans. 



Usually compact, of a fine earthy texture, with a smooth 

 feel, and white or whitish color ; also fibrous, white to bluish- 

 green in color. H. = 2-2'5. The earthy variety floats on 

 water. 



ComjjGsition. JH S f Mg 3 Si 4- 1J aq = Silica 60-8, magnesia 

 27*1, water 12* 1 = 100. B.B. infusible, or fuses with great 

 difficulty on the thin edges. Much water in a closed tube. 

 A pink color with cobalt solution. 



Occurs in Asia Minor in masses in stratified earthy de- 

 posits, and is extensively used for pipe bowls ; also found in 



