Topaz. 
14. Topaz? 
[Communicated by the Rev Edward Hitchcock. | 
“s This eccurs in that rich repository of minerals, the Go- 
shen granite, three miles northwest of the meeting-house, 
associated with green tourmaline, cleavelandite, spodumene, 
indicolite, rose mica, and pyrophysalithe. | found a portion 
of a crystal of this mineral, nearly an inch in diameter ; in 
some specimens of this granite, which I collected for the 
other minerals they contained. It is perfectly limpid, 
although when lying 1 in its bed, it has a delicate green tinge, 
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exhibits a lamellar structure ; in all others, it is conchoidal, 
and the lustre is vitreous. It exactly resembles the limpid 
topaz from Rio Janeiro. It scratches quartz, but is itself 
scratched by the spinelle.” 
Remarks. 
Mr. Hitchcock having given me a specimen of the mineral 
_ described ab OVE, and requested me to examine it, I have 
amine a larger piece might have given 
itas high as it is ey stated, for the topaz — that is from 
3.46 to 3.60.* Mr. Hite cock’s specimen scratches not 
only quartz, but beryl; it is_perfectly transparent and 
limpid, and so entirely foliated in its structure in one direc- 
tion, that a little jar causes it to split into thin, jpaseies 
pieces, with brilliant and beautiful surfaces, while the cross 
fractures are in every direction conchoidal. On comparing 
it with a specimen of limpid topaz from Siberia, in Col. 
Gibbs’s cabinet, I could discover no difference, except that it 
was less brilliant. A very minute fragment when heated, and 
presented to the fibres of cotton caused a slight movement } 
but I could not be positive that it was an electrical effect. 
When exposed to the flame of the compound blow-pipe, it 
readily melted with strong ebullition, and produced a glisten- 
ing white enamel. It will be remembered that this was pre- 
* cisely the effect which I produced by the compound blow- 
pipe upon the Saxon topaz in 1812, several years before Dr. 
Clarke’s experiments were made.—Eprror. 
the specific gravity of a perfectly limpid white topaz from Sibe- 
ria, the weight of which was 431 grains, to be 3.69—from Col. Gibbs’s cabi- 
net, the same mentioned above, 
