Topaz of Connecticut. 198 
or yellowish, or reddish yellow, like that of the Brazilian and 
Saxon topazes, but more generally this topaz is nearly or 
quite colourless, like the topazes of New-Holland and 
Siberia, and the fragments are often perfectly limpid, so that 
in thin slices, they are as transparent as the most perfect 
glass or rock crystal, and when laid upon writing it is per- 
fectly legible through them.* The cross fracture, at right 
angles to the axes of the prisms, is invariably foliated, and the 
substance is neatly divisible into thin slices, with two smooth, 
parallel, and highly brilliant and polished surfaces. This is 
seen, in a degree sufficiently conspicuous, in the most ordina- 
ry and weathered specimens, when broken at right angles to 
the axis, and in the more perfect ones, the brilliancy of these 
interior surfaces is not surpassed by that of any —— 
whatever. e same weet = y taiBihey are often 
served in fragments, that do. t present any external nee 
metrical form. The pee in all directions, 
that which has been described, is conchoidal ; sometimes flat 
and sometimes perfect,, and deep, and peor the wrinkled 
Emre, usually characteristic of that variety of fracture, 
when m erfect. The conchoidal surfaces are likewise 
brilliant,. “5 scarcely yield in Iustre, to the foliated ines 
the lustre ts highly vitreous and sometimes verges 1 
the adamantine. 
Two or three years since, Dr. Brewster of Edinburgh 
transmitted to us an interesting printed paper,t on the “ Dis- 
tribution of the colouring matter and on certain peculiarities 
structure and optical properties of the Brazilian 
topaz.” In this paper (exhibiting that precision and delica- 
cy of observation so pos oie of its — the most im- 
ant circumstance is description, and e: in 
tien: figures, of some eae coloured images and 
regular pictures observed in the plates of the topaz which are 
~ parallel to its natural foliated joints, and at right angles to its 
Ping Our object in adverting to this paper, at this time, is 
— that although, owing probably te the imperfection 
imens, and the want of any precise o 
re lar dispositions of Sold, corresponding with the exter- 
a and internal form and structure of the crystals, have not 
* Through in clined surfaces, aber: iy a distinct double refraction. 
+ Communica’ _— by him to, the Cambridge Philosophical Society, and 
extracted from their Transactions for Vee 
VOL. L—No. I. 25 
