222 PRECIOUS STONES.
Spodumene
may be distinguished from other yellow-green minerals which are doubly
refracting, as follows: Beryl is distinctly less dense, Chrysoberyl and
Olivine are distinctly more dense, and Diopside is slightly denser.
Beryl and Chrysoberyl are harder. Diopside is not so hard, Olivine is
of about the same degree of hardness, but both Olivine and Diopside are
less markedly dichroic than Spodumene, and so is Emerald, which can be
further distinguished from Hiddenite by the Emerald having a colour
more pure and intense. Kunzite and Amethyst may be of nearly equal
hardness, but Amethyst is of lower Specific gravity, and is less
markedly dichroic. Oriental Amethyst (Corundum) while strongly
dichroic, is very much denser than Kunzite, and very much harder.
Various colours of Garnet and all glass imitations may be distinguished
from Spodumene by their single refraction.
328. Jadeite.
This
mineral, which is really one of the Pyroxene group, is often, with its
variety Cbloromelanite and the Amphibole mineral Nephrite, spoken of as
Jade; thus this term includes two distinct species of mineral.
Jadeite
is only known massive, though it has a microscopical crystalline
structure, and is supposed to be either monosymmetric or triclinic. The
masses show an intimate fibrous structure which renders the mineral
remarkably tough and hard to fashion. In colour pure specimens are
almost white, tinged usually with apple-green streaks; sometimes it is
seen of an emerald-green colour or leek green. It is translucent to
sub-translucent in thin pieces, and in the mass opaque. The lustre is
sub-vitreous to
