BLACK CRYSTALtlZED AtJGITE. 5|4^ 



lateral edges of the prism f. Mr. HKiiy has described this 

 species under the name of pyroxene, the chief varieties of 

 which are X\\e bisunitaire and the triuniiaire. 



The surface of these crystals is smooth, sometimes shin- 

 ing, at other times only partly so. Interiorly they have a 

 very glassy lustre. 



They are hard, easily broken, and their fracture perfectly 

 conchoidal. When rubbed to powder their colour is a green- 

 ish gray. 



Their specific gravity is 3*4. 



Before the blowpipe, on charcoal kept at a red beat, the Treated with 

 angles and edges ultimately become rounded. ^^ owpipe* 



A a. A hundred grains, reduced to an impalpable powder. Analysis, 

 were heated red hot with twice their weight of caustic potash. 

 The matter did not enter into fusion. It was of a brown 

 colour, and gave a slight green tinge to the water, with which 

 it was diluted. On supersaturating the liquor with mu- 

 riatic acid, a complete solution was obtained. On evapor* 

 ating to dryness, and redissolving in water, the silex was gjjgj^ 

 separated. After being heated red hot, it weighed! 48 grains. 



b. The solution was? precipitated by ammonia; and the 

 brown precipitate, while still wet, was boiled in a caustic 

 lixiviuna. The alkaline liquor, mixed with muriate of am- Alumine. 

 pjonia, let fall alumine, the weight of which, when purified, 



was 5 grains. 



c. The bro\vn residiuum was dissolved in nitric acid, the Oxide of iron. 

 SQlution diluted with a great deal of water, and carbonate of 



soda added. The oxide of iron precipitated^ and heated red 

 hot, weighed 12 grains. 



d. The supernatant liquor was decomposed at a boiling Oxide of mail- 

 heat by carbonate of soda. The precipitate obtained, and gane^e. 

 heated red ho^, weighed I Of grains. It had assumed a red- 

 dish colour. Being dissolved in nitric acid, it left behind 



oxide of manganese, weighing pne grain after calcination. 



e. As the nitric solution appeared to contain magnesia and / 

 lime, oxalate of potash was poured in, ti!l no. farther preci- 

 pitate ensued. The oxalate of lime, collected and heated j j^^^ 



•f The places of these two edges are occupied by trapezoidal facets 

 ^n t^e Wiv^nitary varietyj the prism of which has eight sides instead of 



