Another form of calcite which is to be sparingly found is what is called
dogtooth spar, having the form shown in Fig. 4. They occur in clear
wine-yellow-colored crystals, from a quarter to half an inch in length;
they occur in the chlorite in geodes of variable sizes, but generally
two and a half inches in diameter, and which, when carefully broken in
half, showed beautiful grottoes of these crystals. The few of these that
I have found were in the four-foot vein of chlorite down the Shaft No.
1, to the west of the shaft about one hundred and fifty feet, and on
the south wall; it may be readily found by probing for it, and then the
geodes by digging in. There need be no difficulty in finding this vein
if these conditions are carefully considered, or if one of the miners
be asked as to the soft vein. Both these forms of calcite may be
distinguished from the other minerals by first effervescing on coming
in contact with the acids; second, by glowing with an intense (almost
unbearably so) light when heated with the blowpipe, but not fusing.
Their specific gravity is 2.6, or near it, and hardness about 3, or
equal to ordinary unpolished white marble.
_Natrolite_.--The finest specimens of this mineral that have ever been
found in Bergen Hill were taken from a bed of it in this tunnel, having
in its original form, before it was cut out by the tunnel passing
through, over one hundred square feet, and from one-half to two and a
half and even three inches in thickness; it was in all possible shapes
and forms--all extremely rare and beautiful.
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