SILLIMANITE. 153 



rocks, and frequently contains crystals, grains, or compound 

 nodules of various other species. Precious Serpentine, hi 

 particular, is often mixed with granular limestone. The 

 different varieties of Serpentine are met with in Saxony, 

 Silesia, Austria, Hungary, Stiria, Italy, Corsica, Sweden, 

 in England and Scotland, and other countries. It is turned 

 on the lathe into vases, and also worked into different or- 

 naments. 



SILLIMANITE. 



SPAR. 



Sillimanite. BOWEV. Journ. of the Acad. of Sc. of Phila- 

 delphia. VoL III. p. 3J5. 



Hemi-prismatic. It occurs crystallised in four- 

 sided prisms of about 106 SCK, the inclination 

 of the base on the axis being 113. 



Cleavage parallel to the long diagonal of the prism. 

 Fracture, uneven, splintery. Surface often 

 rounded, the crystals themselves bent. 



Lustre, considerable upon the single face of cleav- 

 age. Colour dark grey, passing into clove-brown. 

 Translucent on the edges. 



Hardness, superior to quartz or even to topaz. 

 Brittle and easily reduced to powder. Sp. Gr. 

 = 3-410. Electricity or magnetism none. 



It was found by BOWEN to contain 



Alumina 54*1 11. 



Silica 42-666. 



Oxide of Iron 1-999. 



Water 0-510. 



It is infusible before the blowpipe, whether alone or with 

 borax, and is not acted upon by acids. It occurs in the 



