352 Topaz. 
Agr yin’ + le aon £ SO Topaz. 
Ma tiaieas or Yarx Coriecs, Jon. 10th, 1828. 
‘To PROFESSOR SILLIMAN. 
To the interesting ane from the town of Huntington in 
this State, which you recently put into our hands for exami- 
nation, we have devoted as much time and Shatin as were in 
our power, availing ourselves of the instruments.and re-agents 
&c..of this Laboratory, and of your occasional advice and: as- 
sistance. Had yourduties permitted you to examine it your- 
self, its characters would no doubt have been more accurate- 
ly and clearly exhibited, ‘but such as we have found _ 
‘we present them for your disposal, 
1. Crystallization. 
This mineral occurs both massive and crystalline, snibays 
however distinctly foliated in one direction. The crystals 
are either four or eight-sided prisms. The largest crystals 
are four-sided, and the angles of the base oblique; but not 
to be measured with ‘ac accuracy, on account of their 4 
ne ‘In no instance have we fou nd a | sufficiently per. 
“fect* See Hania its: —— ‘though some of ‘the termi- 
A fra t of an eight sided prism, 
as fou ab. oy a Peon goniometer to measure as follows: 
The two mostiacute angles, each  -  « 92° 
Thetwo next less acute, do. - - a 
The four most-obtuse, do. - 162° 
The measures of the corresponding angles of an Sifaidad 
prism of the topaz, as given by Cleaveland, 2d edition Min- 
eraology, p» 292, are, 93° 6'-~124° 29’ —161° 16'; ‘and when 
we consider that the specimen we measured was quite imper- 
fect, so that it was scarcely possible, without a reflecting gon- 
=. to ascertain the angles nearer than one.or two de- 
