ne 
ee 
pe: 
i 
F 
E” 
Geology and Mineralogy of a part of Massachusetts, &c. 41 
Subsp. Pyenite! 
In Chester in detached pieces of gneiss; colour bluish 
green,—six-sided prisms, terminated by planes, with the an- 
gles truncated—imperfectly foliated perpendicularly to the 
axis, lustre of lateral planes vitreous—infusible, sp. gr. to- 
wards 4,.0—less hard than Beryl which it resembles—larg- 
est crystals an inch and a half long, and half an inch in di- 
ameter,—several prisms sometimes united parallel to each 
other. Emmons. 
ia 
6» SILICEOUS SLATE. 
ie : 
In rolled masses in Berkshire county. In beds in trans- 
ition argillite, Troy, Hudson, &c. 
Var. Basanite. 
In Williamstown —rolled pieces. 
o 
* poe 
mei 
oom 
Of various colours, along the eastern range of mountains. 
Sometimes green at Cummington. Porter. 
Var. 2. Prismatic. 
y orthington. The fibres are often “as delicate as those of 
anthus.” This mineral, found also in Saratoga coun- 
sfore rare, has now become plenty, 
Var. Plumose. 
This name which has often been applied to some varieties 
of mica, is intended as descriptive of the mineral. The fi- 
bres are not easily separable, like the prismatic, and diverg- 
Vou. VIII. No. 1. 6 
