Opals are for October – opal is the October birthstone. The Ancient Greeks believed in the supernatural properties of this precious stone – not just for those born under this sign, but to anyone wearing it. It is no surprise as this stone has amazing internal fire. Opals create an iridescent display of colors as they refract light through microscopic spheres that create this fiery effect.
Opal is a gemstone that has a characteristic play of rainbow-like colors. It is a relatively soft (5.5-6.5) stone that’s 3-30% water. Opals are sensitive to pressure, hard knocks, heat.
There are several types of opal:
White opal is white or a very light color with a characteristic color play
Black opal is precious opal with color play. Black opal can be dark gray, dark blue, dark green, or dark gray black and is less common than white opal.
Boulder opal is a precious opal with a dark base and color play. It occurs as pebble rock where opal fills in hollows in another stone
Jelly opal is bluish-gray precious opal with minimal color play
Crystal opal is transparent with strong color play on a colorless, vitreous surface
Harlequin opal is transparent to translucent precious opal with mosaic like colors patterns. This type of opal is found in Australia, Brazil, Central America, Mexico, Russia Nevada and also in Idaho
Fire opal is an orange color in a matrix. This opal is very sensitive to any stress. Fire opal is found in Mexico, Guatemala, Australia, and the US.
This information is from Gemstones of the World – Walter Schumann; published by Sterling Publishing NY
Opals and opal jewelry require more care than some other stones. You should remember to remove your jewelry before bathing, engaging in sports, working in the garden, or cleaning house. Opals should not be exposed to chemicals and cleaners. Wash your opal jewelry in warm soapy water – do not soak the opal and don’t use an ultrasonic cleaner.
Some opals are just incredible stones. One is the Belemnite “pipe” – an opal formed over millions of years in the skeleton of an extinct ancestor of the modern cuttlefish – was dislodged while digging into the workings of an old mineshaft in Australia. There was a thick skin on it, but cleaning it with a grinding wheel revealed its true significance and the wonderful depth of colors. It’s now known as the Virgin Rainbow and has joined a museum collection of opalised fossils from the inland sea which once covered outback South Australia.