Gems : Opal

Opal, the birthstone for October, is one of the most fascinating and varied gemstones in the world. It is the most colourful, although certain forms are colourless. It can be very bright and beautiful, or dull and dead. It is best known for its flashes of colour, although some opals have none. It can be called black, even though black opal is in fact blue, and it can be white. Its best known attribute, the brilliant flashes of many colours, are not called opalescence, but iridescence.
Some people think opal is unlucky, but this is an error dating back to a misunderstanding of a novel by Sir Walter Scott. In fact, it can be one of the most valuable and desirable of gems.