Black + Dark Opal, Natural Opal Type 1, Body Tone N1 to N6
The definition of dark opal is any opal with a body colour dark
enough to enhance the contained or overlying spectral colours.
Any shades from black to light grey, very dark brown to light
brown or dark to light amber would classify as dark opal
irrespective of the origin of the opal. Most boulder opal is
classified as dark opal.
Dark Opal is commonly called Black or Semi Black Opal. Most
black opal originates from Lightning Ridge while semi black with
a background colour from dark to pale grey can originate from
Lightning Ridge, Mintabie (S.A.) and Coober Pedy (S.A.). Opal
with a translucent or transparent dark brown to amber body is
classified as dark opal or commonly 'black crystal' opal.
Black opal from Lightning Ridge is the pinnacle in terms of
price, of all the opal. The finest examples can exceed AUD
$20,000 per carat retail. However, stones of this grade are
rare, hence the price.
Commercial quality forms over 98% of production where prices
range from an affordable retail of $20 per carat upwards,
averaging around AUD $500 per carat retail.
Black Opal forms less than 15% of the total production from
Lightning Ridge. Dark opal, from dark grey to pale grey base
colour form around 60%. While the balance is Light Opal (crystal
and translucent) and 1 or 2% Black Crystal.
Black Opal itself has a body colour of jet black to very dark
grey, these and only these body colours can be classified, Black
Opal. Dark to light body colour is classified as Dark Opal.
As can be seen from the production percentages, Black Opal is a
rare gem, total production annually may be similar in carats to
the famous pink diamonds from Western Australia. The most
expensive commercial gem in the world, where prices can exceed
retail over 1 million dollars per carat.
Although its not envisaged Black Opal could reach this price,
current price levels make it a bargain, particularly considering
the declining levels of production. Most new discoveries of Opal
in the outlying satellite fields of Lightning Ridge are dark
opal not Black Opal. The bulk of Black Opal comes from Lightning
Ridge itself plus areas to the west and NorthWest within a
radius of 20 km from Lightning Ridge. This area is the most
intensely prospected, the production comes from isolated pockets
missed by miners and the working of old mines originally classed
as worked out. There has been no discovery of a new field
producing true black opal for many years. I repeat, at current
price levels, true Black opal is a bargain, even at prices 3 or
4 times the current level it would still be a bargain.
Light Opal, Natural Opal Type 1, Body Tone N7 to N9
The definition of Light Opal is any opal having a pale colour
background which does not enhance the contained or overlying
spectral colours. The background can be a pale shade of grey,
brown, yellow, amber or even green, plus white.
Most Light Opal originates from the South Australian fields but
is also produced at Lightning Ridge where light crystal opal is
Boulder Opal, Natural Opal Type 2 and 3, Body Tone N1 to N9
The definition of Boulder Opal is any opal having a sedimentary
ironstone back with a naturally adhering face of opal silica
which can range in colour from crystal clear to cloudy or milky
and into a light yellow background containing the spectral
colours. Boulder Opal can be dark opal or light opal and when
the face is light or white is valued as a light opal but when
dark, normal boulder values apply.
Boulder Opal is traditionally cut baroque or free-shape with a
baroque face. Baroque boulder opal is traditionally priced per
piece. There is no assessable way to do this. Most are priced by
eye relative to known sales.
Boulder Opal can however be priced by the carat and the written
methods can completely support the valuation at any level of
selling. Boulder is currently the opal with the most sales
appeal and in particular should have a written basis of
valuation along with all other opal. One hopes that this program
may assist in achieving this. Boulder Opal with a light opal
face is valued under the normal Light Opal category.