34 Geology and Mineralogy of a part of Massachusetts, &c. 
6. Concreted Carbonate of Lime. 
Stalactites, stalagmites, and incrustations, in the caverns 
of limestone. See the Geol. Sketch. These are highly 
crystalline, of a dirty white. Between the layers of the 
calcareous rocks in New Ashford and Lanesborough, 
earthy incrustations of carbonate of lime are frequent. 
They sometimes form small elevations, or rise in stalactites 
half an inch lon 
Calcareous tufa, deposited from springs in Williamstown, 
and in quantity from thatof New Lebanon. The latter of- 
ten presents fine ‘ania and verrucose forms. tt has 
often been deposited about vegetables, which have eptinals 
decayed and left only their exact om: 
7. Argentine. 
Sicenifol—Gonthampicn mine and Williamsburgh, just 
beyond the eastern limits of the map. See this Journal, 
Vol. VI, and VII. In Williamsburgh, it occurs in com- 
paratively large masses—decrepitates and phosphoresces on 
a hot iron, like that from Southampton. 
8 Magnesian Carbonate of Lime. 
Associated especially with the west range of primitive 
limestone. Most of the limestone in Pittsfield, Lenox, and 
Stockbridge, is of this variety—coarse and fine granular, 
white and gray, with a foliated fracture. In Sheffield, it is 
often fetid, a new variety. 
Var. 1. Rhomb Spar. Bitter spar. 
In separate small crystals on gray limestone, Williams- 
town. In roundish masses in the steatite of Middlefield 
with green tale. Some of it is of a fine white, close 
grained, and so compact that the rhomboidal tendency 
is scarcely discernible ; other specimens differ only in 
the distinctness with which the fracture shows the multi- 
tude of rhombs which compose the mass. Lustre some- 
what pearly and shining. Other specimens are yellowish 
