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.

Black Crystal

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.