My appreciation and love for opals came rather late. As an Australian, the opals I was used to seeing were the souvenir store varieties: oval or round doublets and triplets set in standard 9ct gold or silver mounts, designed to sell fast to the crowds of tourists. I did not ever think that the opal could be such a wondrous and fascinating mineral with extraordinary beauty. It was whilst on an extended overseas working holiday that I encountered the boulder opal. I was hooked pretty hard and fast.
Scientifically speaking, opal is a hydrated amorphous form of silica (SiO2·nH2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Because of its amorphous character, it is classed aa mineraloid, unlike crystalline forms of silica, which are classed as minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock being most commonly found with limonite, sandstone, marl, basalt and ironstone.
Opal does occur in other countries, like United States, Mexico, Brazil, Africa and central Europe. However, my focus here is on Australian opal which is the most renowned for its stability and magnificence.
Recently, we went to the source of Australian Black Opal, that is, Lightning Ridge. despite what most would see and probably believe, from reality TV shows, opal mining is every bit as challenging as mining for any other precious mineral. The terrain is tough and they work is tougher, even with the use of excavators and mechanical hammers. It is not unusual for a miner to pay for a claim, buy or hire all the necessary equipment and start digging for years before finding anything of high value.