Posted 5 years ago
This is an extremely unusual 12 x 10mm 3.5ct Coober Pedy Opal in a 14k white gold Art Deco ring, set with 24x single cut diamonds.
The opal exhibits a true cat's eye displaying the full spectrum of colours, and the cat's eye holds up well when the ring is turned a complete 360 degrees. A cat's eye like this is very rare in an opal of this size.
The cat's eye in this stone is caused by fine threads of opal material packed densely together, and running in parallel throughout the translucent crystal opal potch.
In many respects this stone looks like the best Ethiopian Welo opal, however it doesn't have Ethiopian opal characteristics. It is totally non-hydrophane (does not absorb water), and it doesn't change colour, translucency or weight at all after being soaked in water or being left in a dry environment for long periods of time.
I bought this piece from a market seller from whom I've got many bargains. I'm ashamed to say I didn't believe him when he was adamant it was an antique Australian opal and I beat him down mercilessly on the price. In my defense, the stone was badly abraided on top and didn't show the cat's eye or its true colours.
However when Opal Pacific re-polished the stone the colours and the cat's eye popped up out of it, and they advised the opal was certainly Australian, probably from Coober Pedy.
Apparently during the polishing process Ethiopian and Australian opals behave completely differently, and the identification was confirmed by soaking the stone in water for days without any change in colour or weight.