Black opal specimens direct from the opal mines at lightning ridge. Mineral display pieces have been a huge market over the last 10 years but black opal specimens have only recently been discovered by mineral collectors. This has been due to the expensive price of black opals, so if a bit of fire colour was seen in rock the miner would expose this colour and most times wreck the opal specimen.
Compared to other minerals and gemstones mined where the miner can take days to manually dig the specimen out carefully and then trained staff would clean the potch or stone that the mineral is formed in and this can take weeks or months of careful work.
Also it is hard to find colour on natural black potch so most specimens are dull colours from black to semi black or grey with inclusions and host rock. The majority of specimens will have sand or potch in the face and if clean they are very valuable. So if a miner sees colour bar on side rock his natural reaction is to break it open or saw blade to expose if it is colour bar.
A clean faced specimen could be cut for stones and many have been in the past as stone prices have been more than specimen value. But this market is changing and unique shapes can be worth more than the stone price.
Opal miners now know that collectors want unusual and unique specimens and in future we might see greater range of these direct from the opal miner.