Some beautiful material came from Eastern Europe and some is still found there, but it is hardly plentiful. Virgin Valley, Nv. has extensive deposits and before the discovery of opal in Cobber Peady, Australia Spenser, Idaho was the world's largest known supply. Brazilain is highly coveted. A rich translucent, often gold colored material which is rare and unfortunately mostly mined out in known deposits. It tends to be more brittle then Australian. Much material comes from Mexico and Honduras as well. Each country's stone has it's own signiture value. Easily IDed by the opalholic.

It could be mentioned as well that, perhaps a bunch of jewelers started the rumor after cracking a few of the precious stones in an attempt to prong set the little devils. One slip of the graver and presto, you a a pile of silca chips. I've done it a few more times then I'd care to remember, offhand.

People are always asking me about the chemical composition of opal. Simple, it's a hydrated silca. Water that's been trapped in that little piece of glassy stone fo up to 20 million years. It's totally amorphous and has no crystalline form. It's thought that there may be a small amount of twinning present to produce it's radiant colors. It's generally thought that the silca layers were formed with submicroscopic layers or films. In other instances it is formed by ancient creekbeds that ran heavily silca bearing water through both dead birds and plant material. With time as the waterlogged material opalized it retained the original form of the plant or bird. Much Mexican opal is opalized bone. Some of the world's most spectacular material comes from Virgin Valley, Nevada. This is almost always wood replacement opal. I've seen and dealt in specimens that are complete branches from ancient trees. Millions of years old.

It's wise to remember that opal is anywhere between 2 and 20 percent water. I've seen so many people ruin stones by treating them with mineral oil. This concept I've never understood. OIL AND WATER SIMPLY DO NOT MIX. Treating the stone with oil is a proverbial bad thing. I've guessed that, perhaps, this notion came from people seeing what used to be the common shipping medium, glycerine. Glyercine does no harm to the stone, but then again doesn't do it any good. Plain water is the best storage solution for rough and cut stone. It's never hurt a single stone and may very well help in keeping the material hydrated.

One last note on this little overview of opal never store your precious and expensive stones in a safe deposit box. Those things are barometricly maintained to as close to zero humidy as possible. Good for paper, bad for opal. If your're interested in cutting the stone I have extensive experience and the webpage will expand to cover grinding and polishing as well.