|
Ant-like mounds provide relief from
the shimmering, dry Coober Pedy landscape. The opal hunter's
refuge from the blistering Australian sun.
Underground, a solitary helmet beam
pierces impenetrable blackness to land upon a much worn rock
face eaten away by the expectant labours of the miner. The
pick strikes and more rock is loosened. This time is different.
The pulse quickens and callused hands tear away more earth
as fiery shafts of colour leap through the cool blackness,
and dance brilliantly tot he beam of the lamp.
The miner has discovered the
light of the Australian opal.
Opal is an extremely rare gemstone
and for this reason is precious. Opal is a gem produced by
nature in a process which has taken millions of years. From
the opals mined today only a small fraction is judged to be
gem quality.
Australia produces 95% of the world's
natural precious opal supply.
Opal is Australia's national gemstone.
The Technical Bit - Opal, a
mineral consisting of hydrated silica in the gel state. Opal
has a hardness of between 5.5 and 6.5 and a relative density
of 1.9 to 2.3. The fracture of the mineral is conchoidal,
and its luster varies from white to black, and in transparency
from transparent to opaque. The special feature of the gem
is the play of prismatic colours that change with the angle
of observation.
The value of any opal is determined
by the colour, clarity, cut, carat weight and pattern of the
colour.
Colour - the strength and purity
of an opal's colour is of prime importance. There is no established
"right" or "wrong" colour, only more valuable. Red colour
makes the stone per carat more expensive.
Cut - the cut of a gemstone
is of extraordinary importance. The proper cutting emphasized
the richness of the gemstone's inherent colour, and also increases
the durability of the stone. The cabochon cut is ideal for
the opal, from the thin or flat cut.
Clarity - while the clarity
of the gemstone is an important feature, it is equally important
to remember that completely "flawless" gemstones are very
rare. Inclusions are inherent to practically every gemstone
and are nature's way of adding variety and individuality to
a gemstone. Always check for internal fractures that reach
the surface since these may affect the durability of the gem.
However, the fewer the inclusions the rarer the stone will
be.
Carat Weight - larger stones
are priced higher per carat than smaller ones because of their
comparative rarity. Remember 1.00 ct of opal weight equate
to 0.20 gram. It is not a quality rating as in gold.
Pattern - play of colour or
movement of the colour in the stone. Also the intensity or
brilliance of the play of colour. The pure spectrum colours
should be of maximum brightness and clarity, giving a "sharp"
appearance. This property is bound up with transparency of
the body of the opal substance. "Crystal opal" is the term
applied to the highest quality in this respect.
|
