Being a sedimentary opal, it is the most stable of all
It will stand difference in ambiant temperature without being affected.( unlike some other opals who need to be kept in a humid environment, or even in water, to stop them from cracking or crazing).
It is also the hardest of all opals and does not crack under normal circumstances.
There is no need to keep it in water or keep it moist like most volcanic opals.
Despite claims made by some opal merchants, any so-called boulder opal found in any other country than Australia, is not a true boulder opal.
Australian boulder opal is found in cracks or cavities of various thickness, in a ferruginous (containing iron) rock, called ironstone.
Australian boulder opal is cut with leaving a thin layer of the mother rock on the back of the opal seam.
It is a very versatile opal as large boulder opals with little opal in it, are carved into very artistic pieces.
When cut and polished, by world standards, it is a "Natural opal,Type 2".