Geology and Mineralogy of a part of Massachusetts, &e. 39 
6. Cacholong. 
On hornstone, and chalcedony in Hinsdale. | 
7. Siliceous Sinter. Hyalite. 
Occurs in serpentine in Middlefield. Emmons. It 
sometimes is nearly stalactitical, Porter, and isofa dirty 
brown colour. 
8. Opal. 
s found in Hinsdale. Ferruginous opal in 
Middlefield. *eanche conchoidal, smooth —texture com- 
pact—colour reddish brown with whitish spots—lustre re- 
sinous and shining—fragments splintery—resembles and 
differs from ferruginous quartz. Emmons 
9. Hornstone. 
Dark coloured in Williamstown. Dark blue in Ser- 
pentine at Middlefield. Emmons. Yellowish and cover- 
ed with cacholong, at Hinsdale. I have received a speci- 
men from N. Carolina, which exactly resembles this. 
10. Burhstone. 
Washington. See Geol. Sketch. 
11. Jasper. 
Red, striped, bluish, in small rolled masses through this 
Section, Green jasper, at Troy. Eaton. 
12, Agate. 
Found in Middlefield and Chester, not very abundant. 
It consists of a ground of yellow jasper, with bands of blue- 
ish white chalcedony. One specimen weighed almost two 
hundred pounds. Emmons. It seems to be one vast 
agate, composed of a multitude of small ones. Some of 
these have been broken out, of a spheroidal shape. Sec- 
