|
Kunzite
This is the violet pink, transparent variety
of spodumene, named after the American mineralogist G.F. Kunz,
a noted gem expert active at the turn of the century.
Appearance The characteristic
color is a violet pink, which can be quite intense. It has
marked pleochroism, seen as a clear difference in depth of
color in different crystallographic directions, rather than
a color change as such. The crystals used as gems generally
have few inclusions and good transparency. Plane surfaces,
looking both specular and transparent at the same time, can
sometimes be seen on the inside and are the warning signs
of cleavage. In fact, its easy cleavage makes this gem quite
brittle, sensitive to knocks, and therefore unsuitable as
a ring stone. It is usually given a (sometimes quite elongated)
oval mixed cut, a pear-shaped or triangular mixed cut, or
even a step cut. Although it is often found as large crystals,
the smaller section of the crystal is used for cutting, the
strongest, most valued color being perpendicular to this surface.
Gems several carats in weight are not uncommon and some of
200-300 carats have even been cut as museum pieces.
Distinctive features Some pink stones look
very much alike: e.g. kunzite; pink topaz, and morganite.
Kunzite, however, has the strongest pleochroism, best seen,
of course, in larger, richer-colored stones. It has much clearer
birefringence than the other two minerals, a factor easily
established in larger stones, with the aid of a lens, by the
presence of a double image of the back facet edges. Kunzite
is also somewhat less hard than the others. This can be established
by touch, the less acute facet edges feeling almost oily or
soapy if rubbed between forefinger and thumb. Pink tourmaline
can sometimes also look like kunzite. In this case, there
is no appreciable difference in birefringence and the pleochroism
can be vaguely similar. The physical properties are also quite
close, but are nonetheless sufficiently different to establish
the distinction.
Occurrence Kunzite is found
in the United States (in various parts of California, source
of the largest crystals, Maine and Connecticut), Brazil, and
Madagascar.
Value Not very high; as secondary
gems go, it is more or less on a par with good quality red
garnets. Gems several carats in weight are common; small stones,
especially pale ones, are of very limited value.
Simulants and synthetics It is mainly imitated
by pale pink corundum. It is not synthesized, at least not
commercially.
|
