Crystal cabinet
Opal
Opal, hydrated silica, a mineraloid rather than a crystalline mineral. Precious opal shows play-of-color; common opal does not.
Precious opal has a pale, dark, or translucent body and patches of spectral color that move when you tilt it, because of the way tiny silica spheres diffract light. Common opal is the same family without that show, often milky, pink, blue, or yellow. Ethiopian rough can look sandy and brown until it is wet or cut, which tempts bad care; a flat holographic sticker look with no depth is a reason to suspect glass or a triplet cap.
What it actually is
| Name used here | Opal |
| Mineral or material | Opal, hydrated silica, a mineraloid rather than a crystalline mineral. Precious opal shows play-of-color; common opal does not. |
| Hardness | About Mohs 5.5 to 6.5, varying, and brittle. Assembled doublets and triplets are only as strong as their glue. |
| How it forms | Silica-rich water deposits spheres of silica in cavities and seams, often in volcanic rocks or, in Australia, in sedimentary basins, leaving a few to several percent water locked in the structure. That water is part of the material; it is not an invitation to add more water from a tap, and it is not a potion. |
Trade names and mix-ups
Precious opal, common opal, boulder opal, and black or white opal are trade categories of the same hydrated silica, and Ethiopian Welo opal is mostly hydrophane, porous enough to absorb water and change look. Doublets and triplets are slices glued to a backing, sometimes under a clear cap, and synthetic opal exists. Opalite is usually glass or plastic, not opal.
Care
The famous failure is crazing: a network of cracks if the stone dries out too fast or is thermal-shocked. Do not bake opal on a radiator, do not store it in a bone-dry sealed box of desiccant, and do not soak it as a ritual either. Ethiopian hydrophane opal can suck up water, look temporarily brighter, and also suck up dye, oil, and dirt; do not wet it to show it off, and never drink the water afterward. Do not soak doublets or triplets; water attacks the glue line. Avoid ultrasonics, steam, salt, perfume, and sudden heat. Wipe with a soft dry or barely damp cloth and dry at once. Ordinary room humidity is the care plan, which is wonderfully undramatic.
Provenance
Australian opal fields are the historic modern source and a real mining landscape; Ethiopian opal, especially since the Welo finds became commercial in the early twenty-first century, is largely artisanal and often hydrophane, with treatment and porosity undisclosed. Buy from someone who will say the country and whether the stone is solid, a doublet, a triplet, smoked, or dyed; a curse is not part of the disclosure.
Symbolism
- slow dryness
- color that depends on angle
- ordinary room air
- patience with a crack
Folklore, only where it exists
Pliny wrote about opal with delight, and European crowns later admired stones that mostly came, before Australia, from what is now Slovakia. The idea that opal is unlucky is much younger than those facts. A major push came from Walter Scott's 1829 novel Anne of Geierstein, in which a character's opal dulls and the reading public took a plot device personally, with some help from a shifting gem market. Bad luck is not a physical property of hydrated silica. The Wilde Altar refuses both the curse and the counter-curse that says opal must be soaked, worn, or gifted only under special rules. The care is ordinary humidity and no heroics. Play-of-color is diffraction. You may enjoy it when you tilt your head, which is as participatory as this mineral needs you to be.
Cautions
An original practice
The Ordinary Room
- A solid opal, or a doublet you have already labeled as a doublet
- A dish in a room where people actually live
- A note with the date
- A soft cloth
- 1Set the opal in the dish away from radiators, sunny sills, bathrooms that steam, and any bowl of salt or desiccant.
- 2Write the date and two words about how it looks: bright, quiet, cracked, unchanged. If it is a doublet, write doublet so you do not soak it later in a moment of enthusiasm.
- 3Once a week, look again and add two more words. Do not wet an Ethiopian stone to make the week more interesting.
- 4If you see new cracks, stop handling it so often and do not try to oil, boil, or bless the crack shut. A jeweler can tell you if anything mundane can be done. Often the answer is no.
- 5Put the note under the dish. The room's ordinary air is the whole technique.
Stay in the room we actually live in. I will not dry you out to be careful, or drown you to be kind. Color is an angle, not a fortune.
Leave the dish where it is. No moonlight soak, no oil rub, no salt. If you travel, carry opal in a case in the cabin's ordinary air rather than in a hot car trunk.
A practical action. Add the weekly two-word check to a calendar if you own a stone you are worried about, and insure or appraise a valuable one in the ordinary way.
Substitutions
- A piece of iridescent soap bubble photographed, then the soap washed off your hands
- A holographic paper scrap in a dish, labeled paper, if the point is looking at color play without owning a fragile silica
Beginner questions
- Is opal unlucky? No. The unlucky-opal idea is a modern superstition with a boost from a nineteenth-century novel. It is not a law of silica or of this house.
- Should I soak my Ethiopian opal so it looks brighter? No. Hydrophane opal absorbs water and can stain or craze. Do not soak it, and never drink that water.
- What is opalite? Usually glass or plastic, not opal. It can be pretty. It should not be priced or cared for as hydrated silica.