Honduran opal rough from south America. forms in large blocks of black basalt.
Miner chisels away at these blocks to follow the colour bar and is called black seam or black matrix opal
The black matrix has thick bars of l fire in the matrix so are easy t o cut and polish and the seam opal is thinner veins so most is potch backing similar to boulder .l
As this opal was formed from volcanic ash .there are hundreds of small scale mines in south west but only 1-2 major source so not much rough material gets offered
Some Honduran specimens can be polished a s whole piece or make ,matching cabochon stones that will match for jewelry set
This rough is not treated, many cutters see it similar to treated Andamooka rough but this is natural formation
As with all stone rough cutting mask should be worn and plenty water to run onto your wheels while cutting and vacuum to suck air is also recommended for any cutting and polishing system.
Honduran rough specimens more than 1 cm thick, have a crystal clear, milky white, slightly blue or brownish orange colouration because they are so thin, the gems tend to be cut with the black basalt forming the back of the stone forming black-matrix.