180 Mr. li. Crossley on Algerite, a new Mineral Species. 



which mineral also occurs at this locality. The honey-yellow 

 crystals give a spec. grav. 2*78. Hardness from 3 to 3*5. 

 Brittle, subtranslucent. Before the blowpipe alone it fuses 

 readily to a white blebby glass. With soda it fuses to a dirty 

 white slag. With borax and phosphorus salt it gives a bead, 

 faintly tinged by iron, enclosing a siliceous skeleton. Heated 

 in a closed tube it gives off water which reacts feebly alkaline, 

 and the powder changes in colour from light buff to light 

 brown. It is perfectly attackable by a mixture of sulphuric 

 and hydrochloric acids. 



Crystals of the mineral, carefully cleaned, gave for its com- 

 position — 



Silica 49-96 



Alumina 24*41 



Peroxide of iron . . . 1*48 



Magnesia 5 # 1S 



Carbonate of lime . . 4*21 



Potash 9*97 



Water 506 



100-27 



The amount of carbonic acid directly determined is equal 

 to that in the carbonate of lime obtained. It is therefore evi- 

 dent that the lime is not a constituent of the mineral. 



Deducting the carbonate of lime, and calculating the re- 

 maining members for per-centage proportions, we shall have 

 for the composition of Algerite, — 



Proportion 

 of oxygen. Ratio. 



Silica 52-00 27*00 7 



Alumina .... 25*42 ll-88\ 



Peroxide of iron . . 1 *54 47 J 



Magnesia .... 5*39 2*0s1 



Potash ..... 10*38 1*75 J 



W 7 ater 5*27 468 1 



10000 



The above composition is very well represented by the 

 formula 



3(A1 2 3 , 2Si0 3 ) + (MgO, KO) 3 Si0 3 -f 3HO; 



and there being no previously known mineral which gives the 

 above characters, composition and formula, Algerite must ne- 

 cessarily rank as a new species. 

 Boston, Mass. U.S., April 29, 1850. 



