Opal
Opals are fascinating gemstones. In their ‘precious’ form they exist in so many different varieties: crystal, boulder, white, black, fire, jelly… Common opals also exist: without color fire, coming mostly from South America (the Andes) they are pink, blue or white even sometime green from Madagascar.
Since the 19th century Australia is the main provider of precious opal. Ethiopian opals appeared about ten years ago on the market. This opal is particularly hydrophane: it exhibits a small quantity of water in its structure making it sensitive to its environment. Contrary to Australian opals, Ethiopian opals can change of appearance rather quickly, becoming milky and opaque while it was transparent few days before. That’s the reason why I do not offer Ethiopian opals in my web site.
Opals are made of thin layers of silica and builds up in deserts. The rare desert rains carry on the 
silica dust through the sand and the water evaporating leaves layers of silica in rock cracks. Years after years, the layers of silica grow thicker and fill the rock cracks to form the opal.
Boulder opals are a good example of opal crystallization in its local rock. Boulder opals are harder and heavier than other opals.
You will find on my web site a fine selection of crystal and matrix opals. Do not hesitate to contact me for further inquiries.