associated with Coru?idum. 485 



was so hard as to resist all attempts to penetrate it by hardened 

 steel, greatly impeding the operations of the miners in the 

 chrome iron districts. 



I also received other specimens of the same from Mr. Wil- 

 liams of Westchester, associated with corundum, which was 

 found imbedded in it; and from this circumstance it has been 

 mistaken by some mineralogists for Indianite, which species 

 it resembles in hardness, gravity and in granular structure, 

 but not at all in composition. 



In its granular structure it so resembles dolomite, that no 

 difference can be detected between them by the eye, while 

 its hardness and great difficulty of fracture completely blind 

 the inquirer as to its real character. Its characters are as 

 follows : — 



Massive, compact, granular, resembling while dolomite ; 

 tough ; fracture even, but very difficult. Colour, white with 

 shades of gray. Streak, white. Hardness, 7 to 7*25 (scratching 

 quartz with facility). Gravity, 2-619. 



Insoluble in acids. Before the blowpipe, infusible, and 

 does not colour theJlamei/eUoiso ; with the fluxes yields evidence 

 of silica, alumina and lime. By a quantitative fusion with 

 carbonate of baryta, soda was detected. 



The first specimen analysed was from Lancaster County, 

 Pennsylvania, and showed no trace of corundum disseminated 

 in it. 



This analysis was made by Mr. G. J. Brush, and yielded 

 on the quantity taken, 1-234- grm., as follows: — 



Oxvgen. 

 Silica .... 0-8225 = 66-653 p. c. 34-85=12 

 Alumina . . . 0-2565 20-786 10-70 3 



Lime .... 0*0253 2-050] 

 Magnesia . . . 00071 0-519 V 3*08 1 

 Soda . . . . 0-1155 9-360 J 



3242-47 100-00 



This is precisely the formula and constitution of an albite. 

 The second analysis was on a specimen from Unionville, 

 Chester County, Pennsylvania, having identical characters, 



