The
most treasured variety of opal is black opal with strong play of color,
that is,
brilliant
flashes of different colors. Black opal is so called because of its
dark
background color.
The
variety known as white opal has a light background, and the colors displayed
lean
toward
the pastel hues.
Crystal
opal has a colorless background and exhibits play of color, but, unlike
white
or black opal, it lets light pass through it
Fire
opal is also fairly transparent, but its background color may be yellow,
orange,
red or brown.
Sometimes
it doesn't even have the typical play of color.It's often called Mexican
opal because Mexico is a major source of this type. Fire opal with a red
body
color
is also known as cherry opal.
Opal
that is colorless, transparent to semitransparent and has little or no
play of
color
is called jelly or water opal.
Opal
quality is judged by the number of colors exhibited and the
evenness
of the pattern.
Australia
is the world's most important source of opal. The opal miner is a strange
breed
of individual. He chooses to lead a spartan life in a particularly barren
and dry
corner
of the world while he searches for his rainbows. To escape the extreme
temperatures,
he must burrow a home underground.
Opals
are usually found in sandstone or claystone. Deposits are spread over a
wide
area,
and there is little clue to their location. Mining is done on a small scale
with
hand-operated
machinery and small tools. A pocket knife might be the final
instrument
to loosen an opal from its host rock.
Black
Opal is the rarest and most valuable type. It is generally found as a bar
(or
bars) of various colours forming natural water horizontals in dark
grey
to black 'potch nobbies' or 'nodules'
The unique patterns are as complex as an artist's imagination.Few realise
that
99.9% of the world's supply of this radiant, dark lustrous gem is mined
at only
two tiny pinpoints on the globe - Lightning Ridge and Mintabie.
He who possesses a Black Opal is indeed fortunate!
Boulder
Black Opal is a special type of opal found
mostly in central Queensland. It is a curious formation
of silica which has filled the cracks and crevices in
light and dark brown ironstone boulders. Invariably
stones form Queensland are cut with the natural host
rock (ironstone) left on the back. Sometimes, owing to the thinness of
the opal
seams, the boulders sawn into baroque shapes, and the precious heart of
opal.
Small boulders sometimes containing 'kernals' of opal are known as 'Yowah
Nuts'
after the nearby town of Yowah. Boulder 'matrix' opal is a peculiar opal
formation
where flecks of rich, flashing colours of opal are scattered throughout
the brown
ironstone, like twinkling neon lights of a distant city.
