ROCK TRIVIA: OPAL, Octobers Birthstone
The Opal group includes a large number of gemstones. If Opals lack a play of colors, they are called Common Opal. Precious Opals exhibit fire and color in a wide range of main body color, including dark or black, clear white to milky, pink to orange.
Opal is formed when water runs down through the earth and picks up silica from sandstone, As the water evaporates, it leaves behind a silica deposit. This cycle repeats and eventually - in about about 5 to 6 million years- Opal is formed.
Until recently, Australia has been the source for over 95% of the world's precious Opal. That all changed in 2008 when Opal from Ethiopia became famous for its unusual color patterns. Ethiopian Opals even display colors not found in Australian Opals like turquoise and indigo.They are also the toughest opal available. The Gemological Institute of America performed drop tests of opals from various sources including Australia. From almost 5 foot the opals were dropped onto concrete. Only the Ethiopian opal survived the test.
"Halley's Comet", is recorded in the Guinness Book of Records as the world's largest uncut black opal nobby. This huge Opal was found by a group of miners on the Leaning Tree Claim at Lightning Ridge around the time "Halleys Comet" crossed the Australian skies.It weighs almost 2000 carats!