Crystal opal clearly showing the weight written on the back
of the stone
Crystal opal wherever it comes from is transparent not
translucent and with the exception of Black Crystal and its
background variations, can be established by the following
simple method. A dot placed on the back of the stone using a
black felt pen should be clearly visible from the face. If not,
the stone is translucent or opaque. Translucency is established
by holding the stone up to the light. Translucent stones from
all areas are grouped together.
Two views of a black crystal showing transparency
Black Crystal and its associate background variations are
exempted from the above test due to body colour. They should be
transparent to highly translucent when held up to the light.
South Australian Crystal Opal
South Australian Crystal opal is not a poor relation
to Lightning Ridge Crystal. In fact, particularly in red
stones, it can surpass it in colour tones of rich red, however,
Lightning Ridge Crystal's clarity and purity, coupled with
brilliance and relative rarity, make it the more valuable stone
quality for quality. Most Lightning Ridge Crystal is cut in a
pleasing high dome chunky oval unique to this variety.