As I noticed before, the better plan of
distinguishing a mineral is by being familiar with its appearance, but
as this is generally impracticable, I will detail the modes used in
lieu of this to be applied on bringing the minerals home. These
distinguishments depend on difference in specific gravity, hardness,
solubility in hot acids, and the action of high heat. I will explain the
application of each one separately, commencing with--
_The Specific Gravity_.--In ascertaining the specific gravity the
following apparatus is necessary: a small pair of hand scales with a set
of weights, from one grain to one ounce. These can be procured from the
apparatus maker, the scales for about fifty cents, and the weights for
not much over the same amount. The scales are prepared for this work by
cutting two small holes in one of the scale pans, near together, with
a pointed piece of metal, and tying a piece of silk thread about eight
inches long into these. In a loop at the end of this thread the mineral
to be examined is suspended. It should be a pure representative of the
mineral it is taken from, should weigh about from one hundred grains to
an ounce, and be quite dry and free from dirt. If the piece of mineral
obtained is very large, this sized portion may be often taken from it
without injury; but it will not do to mar the beauty of a mineral to
ascertain its specific gravity, and it is generally only applicable
when a small piece is at hand.
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