As the birthstone of October, the opal is a very interesting stone. Opals are loved by
people for their rainbow colors and translucent prettiness. Opals have been mentioned
throughout history, with reference to them dating back to Roman times when they were
used to ward off bad health by keeping evil spirits away. The vast majority of Opals are
mined in Australia; in fact about 95% of them are mined down under.

As a stone Opals contain a significant water percentage. It is this, which gives them their
rainbow effect. This is a very important consideration if you're buying opals because heat
can affect the quality of the opals by reducing the amount of water in them. In its natural
state, opals come in a variety of colors such as black, white, crystal and a fiery color. The
black opals are the rarest of these and are therefore the most expensive.

When buying opals you should take the following into consideration:

Solidity: Check to see if your opal is a doublet or triplet rather than a solid opal. Doublets
are opals shavings glued to another less expensive material. Triplets consist of a base of
some solid dark material, an opal in the middle and some clear covering surrounding this.
Triplets have significantly lower opal content than solid opals and doublets so beware
you know what you're looking at when you buy.

Patterns and Color: Take time in looking at the color and patterns created by the light and
the stone. The best opals usually have a variety of colors which are widely spread
throughout the stone.

Background Color: The black opals are the most prized followed by the dark green,
brown and gray. Any opals that are more translucent are usually cheaper.

Size and Weight: Like gold, opals are sold using the caret weight system. The more
carats an opal is the more expensive it is. Be careful when buying doublets and triplets as
some bad sellers may try to sell you the total weight of the doublet/triplet as the weight of
the opal.

After you buy your opal stone, you should be careful with how you care you it and clean
it. As already mentioned the stone contains significant water content so don't expose it to
heat. Be careful when cleaning your opal stone as it's a soft stone. The best thing to do is
to gently wipe your stone with oil. After wiping your stone with oil use a different stone
to clean it off.