458 Prof. B. Silliman on some Americati Minerals. 



is to be worked soon for emery, and probably both it and the 

 euphyllite will be obtained there in abundance. This species 

 was also supplied to me by Mr. Williams of West Chester. 



III. On Monrolite, a mineral resembling 



WoRTHITE. 



My attention was called to this mineral by [Mr. Wm. S. 

 Vaux of Philadelphia, who had received it from the locality 

 marked " topaz." It somewhat resembles pycnite in general 

 aspect, but as will be seen is a very different thing. 



It occurs at Monroe, Orange Co., New York, where it is 

 found in a quartzose rock with magnetic iron, pink felspar, 

 black mica, pinite and common garnet. Colour green to 

 greenish gray. Structure radiating in sheafs from a centre in 

 groups from an inch to two inches in diameter. Also in 

 single implanted individuals. Cleavage and form of single 

 crystals resembles Sillimanite. Hardness, 7*25 on an angle ; 

 on cleavage face about 6. Gravity, 3-045, 3*096, 3*07. Co- 

 lumnar, fibrous. The oblique prisms were not measured, 

 being too irregular. 



B.B. alone in tube gives off neutral water. Infusible, 

 whitens ; dissolves slowly in carbonate of soda, readily in bo- 

 rax and in salt of phosphorus, leaves a siliceous skeleton which 

 reacts slightly for iron. 



Its qualitative assay indicated the presence of silica and alu- 

 mina, with a trace of iron and magnesia. 



It was fused with carbonate of potash and caustic potash, 

 and its analysis yielded — 



I. ir. III. 



Silica . . . 40-92 40-389 40-389 



Alumina . . 56-61 55-729 56'6\S 



Magnesia . . '28 '280 -280 



Water . . . 3-09 1-840 2-794 



100-90 98-238 100-079 



These analyses correspond closely with8SiO'', lOAtt)'^, 3H0. 



8 atoms Silica . . 4618-48 = 40-59 per cent. 

 10 atoms Alumina. . 6423*30 56*44 

 3 atoms Water . . 337-44 297 



11379-22 100*00 

 We have then the formula 



8(Alt)3, Si03) + 2Afc)^ 3H0. 

 The Worlhite of Hess gave the formula— 

 5(A103, SiO^) + Alt)3, 3H0 corresponding to his analysis, viz. 



