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272 PRECIOUS STONES.
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by its greater density and more marked dichroism. Tourmaline, which is strongly dichroic, is much less dense.
410. Axinite.
Axinite
is but rarely used as a gem, although it has many properties making it
suitable for such a use. In colour it varies from a pale sherry yellow
to a deep brown
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or
almost plum colour ; the usual tint is clove brown. The lustre is
vitreous, inclining to adamantine in some specimens, and the crystals
are often transparent. It is doubly refracting, the indices in red
light being, the greatest 1*681, and the least 1*672. It shows marked
dichroism, yielding olive green and violet-blue, or cinnamon brown and
violet-blue images in the dichroscope, according to the direction in
which the crystal is viewed. It is pyro-
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