MINERALOGY. 127 
has been found at Bath, Bedford, and Walpole, in small, grayish-white 
efflorescences. It is easily recognized by its astringent taste. It is iso- 
metric in crystallization, but is usually found in mealy crusts. 
89. CatcirE [Ca CO*]. 
Calcite, although abundant enough in New Hampshire, is generally 
found in the massive condition, forming limestones, or, mixed with other 
minerals, forming calcareous rocks: hence its consideration belongs 
chiefly to lithology. Good rhombohedral crystals of calcite are, how- 
ever, found at Amherst, Surry, Warren, and the Notch. The variety of 
calcite called argentine is found at the iron mines in Lisbon. It is called 
argentine on account of its silvery lustre. 
In its more ordinary forms, calcite is widely distributed. It occupies 
veins in other rocks, as at Portsmouth, where it usually shows large 
cleavage surfaces, indicating coarse crystallization. It also forms thick 
beds interstratified with the surrounding rocks, as at Orford, Haverhill, 
Meredith, and Littleton. At the latter place it is filled with fossils; and 
the accumulation of beds of limestone is supposed to be largely due to 
the various organisms, whose calcareous shells are so often found in them. 
When the last remnants of this organic life have been destroyed, the 
limestones are white, while otherwise they are blue or gray. 
Calcite is constantly met with in thin sections of some classes of our 
rocks, sometimes as an original component, and sometimes as a second- 
ary product. Asa constituent of the basic eruptive rocks, it has plainly 
resulted from their decomposition, since it is usually found in little cav- 
ities, though it is also scattered all through the rock, as can be proved 
by moistening them with hydrochloric acid, and watching for an effer- 
vescence. Such minerals as pyroxene, by slow acting agencies, give 
up a part of their lime, and are converted into chlorite, while the basic 
feldspars quite easily part with theirs, as was shown in the discussion 
of anorthite. Thus results the calcite which so commonly fills all the 
pores of such rocks, and by such processes the lime has been separated 
from the original basic rocks to form beds by itself. 
The microscopic characters of calcite, as seen in thin sections, are 
very characteristic. It is strongly double refracting, and the light 
which passes through a crystal with its vibrations in a plane par- 
