Constituents of various Minerals. 269 



Lustre pearly. When pounded, it appears to be partly com- 

 pact, and partly composed of pearl coloured flakes or scales, ha- 

 ving somewhat the appearance of talc. Lustre shining. 



Opaque, or only slightly translucent on the edges. 



It is softer than calcareous-spar, but harder than gypsum. 

 The nail makes an impression on it with difficulty. 



Specific gravity 2.688. 



Infusible before the blowpipe. 



The specimen was interspersed with iron-pyrites. 



I requested Captain LEHUNT to analyse this mineral, which 

 he did with great care, examining both the compact and scaly 

 portion separately ; but he found the constituents of both exact- 

 ly the same, namely, 



Silica, . ^ .. . . . -. . 72.52 



Alumina, 20.44 



Protoxide of Iron, . . 2.40 



Water, 3.40 



98.76 



If we exclude the iron and water as accidental ingredients, 

 it is obvious that the mineral is Al S 4 , or composed of 



v 



4 atoms silica, 

 1 atom alumina. 



It is therefore a quatersilicate of alumina. 



. f j:niirmiu'lo UEOIII trio* (i 



17. Cinnamon-stone. 



Whoever compares the cinnamon-stone with garnet, will, I 

 think, be under no hesitation about concluding that the two mi- 

 nerals belong to the same species. The crystalline shape of both 

 is the same, the hardness the same, the specific gravity the same, 



M m 2 



