52 Geology and Mineralogy of a part of Massachusetts, &c. 
29. CHLORITE. 
Deep green-structure distinctly foliated. Middlefield and 
Chester, in smal] masses, and also mica-slate. Emmons. 
Among the older primitive rocks, chlorite seems to be 
composed of more distinct folia. Also, in the vallies on 
both sides of the Taconick range of mountains. The com- 
mon var. 1s very abundant in Williamstown, associated with 
quartz. Itis found along the Hudson also. 
Chlorite Slate. Abundant in Williamstown and Peters- 
burgh. Also in Pownal, Great Barrington, and in various 
places in Rensselaer and Columbia Counties. . 
30. GIBBSITE.* 
Discovered by Dr. E. Emmons in an iron mine in Rich- 
mond. It occurs in incrustations and stalactical and ma- 
millary forms, partially crystallized. In Lenox, small 
mammillary bodies upon brown hematite. Most of it seems 
to be composed of radiating fibres. It is also diffused 
through disintegrating quartz. Besides these forms, it is 
found compact and earthy, resembling an indurated clay, in 
the same mine in Richmond. . 
31. ARGILLACEOUS SLATE. 
[See the preceding Geol. Sketch.] 
The var. Aluminous Slate occurs in Pownal in argillite. 
Also in New Lebanon and Troy ; Eaton. 
Graphic Slate, in small quantity with argillite in Lanes- 
borough and Williamstown. Abundant at Bennington ina 
hill of argillite. See the Geol. Sketch. When this mine- 
ral is thrown into melted nitre, carbonic acid is rapidly ex- 
tricated, as from charcoal or plumbago in a similar situa- 
tion. 
Glazed Slate. Troy, &c. Eaton.—See the preceding 
Geology. 
- May not those minerals, which are composed of the nearly pure earths, 
with propriety be arranged in a separate class. 
