MINERALOGY. 443 



Asbestus is only a fine crystal variety of hornblende 

 ( Tremolite) ; made up of delicate, hair-like fibers, but 

 so interlaced lengthwise that their structure is scarcely 

 apparent ; blades, are flexible, elastic, silky, soft ; trans- 

 lucent, occasionally opaque ; smooth to the touch. Color 

 mostly whitish, but often of various shades of green, 

 verging into brownish-yellow ; occurs in narrow seams or 

 blades in gneiss, mica slate, etc., in the mountains of 

 Savoy ; also in hilly regions of the eastern and middle 

 parts of the United States. There is a coarser variety, 

 less silky, fine, and elastic, which is called common asbes- 

 tus, mountain leather, and mountain cork. 



Amianthus which includes Ligniform asbestus, is com- 

 posed of slender fibers, with a rich satin luster. These 

 filamentous fibers, easily separated, can be spun and 

 woven into incombustible cloth ; the ancients used it for 

 the wicks of lamps in their temples ; also for enveloping 

 the corpses of the dead which were to be burned, as, 

 proof against all igneous action, the ashes remained un- 

 changed and unscattered. 



IY. Baryta Strontla Sulphate of Barytes, or 

 Heavy Spar occurs either in the form of crystals or is 

 of massive, compact, granular, fibrous, or coarse lamel- 

 lar structure and is distinguished from Celestine and 

 Arragonite by its uncommonly high specific gravity. 

 Luster vitreous ; feels somewhat oily ; translucent, passing 

 into pearly. Colorless mostly, although often found of 

 various shades of gray, yellow, and brown. II. = 3 to 

 3.5. G. = 4.1 to 4.7. Found in Germany, in the 

 primary and sedimentary rock formations in the Hartz 

 mountains, and mining region of the Black Forest ; also 

 in Connecticut, New York, and Pennsylvania, associated 

 with the metallic ores. Heavy spar is used in many 



