97.576 

 and he considers it as essentially composed of 2 atoms of silicate of 

 lime, and 1 atom of silicate of alumina. 



I have found the xanthite at Amity, Orange county, N. Y. in lam- 

 inated masses in the same rock in which it is disseminated in grains. 

 These masses are very frangible, crumbling readily into grains, some 

 of which can be cleaved into prisms of perhaps gV of an inch in 

 their lineal dimensions. The laminated masses when held to the 

 light exhibit very plainly by reflection, the directions of the cleavage 

 planes. It exhibits double refraction when a candle is viewed through 

 a thin plate of it, by placing it over a fine hole pierced in a card. 

 It can be fused in small particles on a fine slip of platinum foil by 

 the common blowpipe. When in fusion it intumesces, and gives a 

 greenish translucent bead, slightly attractable by the magnet. With 

 borax it gives a glass, yellow when hot, but colorless when cold. 



The cleavages are parallel to the sides of a doubly oblique prism, 

 which is probably its primary form, as no other system of cleavage 

 planes, could be obtained. The reflective goniometer gave for the 



angles 



PonM 



PonT 

 MonT 



The planes M and T were not sufficiently brilliant to give the an- 

 gles exactly ; but it is presumed that the variation is not very great. 



Localities of Minerals. 



Westerly, R. I. — Iron sand on the beach, two miles S. E. of Ston- 

 ington Point. Carnelian, jasper, a chlorite near the same place. 



Sulphurets of iron (pyrites) in small but very perfect cubes, in the 

 fine quarried graywacke at the quarries S. E. of Fort Adams. Jas- 

 per, very fine, at one of the quarries near Fort Adams. 



