You're ready to go shopping for opals. Simply print this page and take it with you to the jeweler's. Ask any questions you need in order to satisfy each item on the list. Not only will your dealer respect your knowledge, you will also take home a stone of unquestionable quality and beauty.

Color and type

1. Black (or dark) opal is the most valuable type and body color.
2. View the stone face-up over a black background.
3. Does the play-of-color maintain brilliance away from light? (Very important.)
4. Intense red is most rare and prized. Blue is most common. The more intense the color, the more valuable.
5. Broad flashes of color make for more valuable opal as opposed to pinpoint play-of-color.
6. Black opal should be opaque. More valuable lighter stones are transparent.

Size, shape, cut and carat weight

1. Oval shaped cabochon (dome) cuts are typically most valuable. But, top quality freeform cuts may cost more.
2. Stones of appropriate size for jewelry settings will carry the highest price-per-carat.
3. Think in terms of price-per-carat rather than total cost.
4. Beware of "total weight" price tags. Don't pay per-carat opal prices for settings.
5. Boulder opal will be sold by the piece, not the carat.

Imperfections

1. Crazing (webs of tiny fractures) is dangerous and detrimental to value.
2. Don't confuse crazing with internal pattern lines.
3. Cracks also dramatically reduce value.
4. Ask about guarantees against crazing.
5. Can you see sandstone from face up? (Not good.) Sediment on the bottom is harmless and does not affect price.
6. Ask how the stone has been stored. Opal thrives best in a cool, moist climate.

Assembled stones, treatments, imitations and disclosure

1. Opal doublets (black opal glued onto glass or lower quality opal) are an inexpensive alternative to naturally formed top quality black opal.
2. Side viewing reveals doubling and tripling.
3. Ask about sugar-acid immersion and wax or plastic impregnation treatments.
4. Get all treatments fully in writing on your receipt.
5. Beware of synthetics and fakes. Always shop with reputable dealers.

Opal is October's birthstone and is also a traditional gift for fourteenth wedding anniversaries.