138 PHYSIOGRAPHY. 



Lustre pearly, distinct upon Pr -f- oo, inclining to 

 vitreous upon the other faces. Colour greenish- 

 white, passing into greenish-grey, and mountain- 

 green, sometimes also oil-, leek-, and blackish- 

 green. Streak white, dull. Translucent on the 

 edges ... opake. 



Very sectile. Hardness = 2-5 ... 3-0. Sp. Gr. 

 = 2-660 of a cleavable compound variety, 2-596 

 of a columnar variety. 



Compound Varieties. Massive : composition 

 granular, strongly coherent. If the composition 

 becomes impalpable, the fracture is earthy. The 

 particles of columnar compositions are very thin ; 

 fracture splintery. 



Its chemical composition is unknown. Before the blow- 

 pipe it is infusible, but gives out water, becomes first 

 black, then white and opake, and acquires a degree of 

 hardness nearly = 5-0. It is soluble in salt of phosphorus, 

 with the exception of a silica skeleton. When heated 

 with solution of cobalt, it assumes a pale red colour. It 

 appears therefore to contain water, silica, and magnesia. 



The cleavable varieties have been found, accompanied by 

 octahedral Iron-ore and macrotypous Lime-haloide, in a 

 bed in primitive rocks. The only locality hitherto known 

 is the iron mine called Engelsburg near Presnitz in Bo- 

 hemia. 



It is likely that many varieties of the common Asbestus 

 of WERNER, (JAM. Syst. Vol. II. p. 156.), particularly 

 that from Zdblitz in Saxony, should be referred to this 

 species. According to WIEGLEB, it consists of 



Silica 46-66. 



Magnesia 48-45. 



Oxide of Iron 4-79. 



