Fire Opal
Fire Opal is hydrated silica (opal), SiO₂·nH₂O. In the hand, it rates 5.5 to 6.5 on the Mohs scale, and it runs flame orange and cherry red. Opal whose BODY is the fire, transparent flame-orange to red gem material, often faceted, sometimes adding green play-of-color flashes.
The geology.
Fire Opal carries the formula SiO₂·nH₂O. It belongs to the amorphous system. Catalogues list it as hydrated silica (opal).
It sits at 5.5 to 6.5 on the Mohs scale. The surface reads vitreous to resinous. Light behaviour is transparent to translucent. Specific gravity runs 1.9 to 2.3. The streak is white. It breaks with conchoidal fracture.
Opal whose BODY is the fire, transparent flame-orange to red gem material, often faceted, sometimes adding green play-of-color flashes.
It reaches buyers as faceted, cabochons, rough in rhyolite matrix or cantera (opal-in-matrix) cabs.
The origins.
Volcanic opal fields: Querétaro and Jalisco (Mexico, the classics), Ethiopia, Oregon (USA).
On value, the database notes: mid-range; clean red faceted Mexican stones are prized.
Traditional associations.
In energy work traditions, associated with creative passion and joyful energy.
We keep this section because people ask. It sits below the geology on purpose, and none of it describes something the stone does.
Spotting the real thing.
Opal whose BODY is the fire, transparent flame-orange to red gem material, often faceted, sometimes adding green play-of-color flashes.
Orange glass and resin sell as fire opal online; genuine stone may also craze over years, ask sellers about stability.
| Looks like | How to tell them apart |
|---|---|
| Carnelian | Carnelian is denser, harder chalcedony with waxy luster; fire opal is lighter and glassier |
| Orange glass | Glass shows round bubbles and feels warmer than its look |
| Citrine | Citrine is hard crystal quartz (7); fire opal scratches with a knife edge |
At-home tests.
Before anyone talks you into a lab report, these are the checks worth doing yourself on fire opal.
| Test | What you should see |
|---|---|
| By weight | Featherweight for a gem (SG ~2) |
| Scratch check | Knife can just mark it |
| By eye | Often grown in pale rhyolite matrix (cantera) |
| By eye | May craze if it dries, keep from heat |
Anything that scratches, burns or dissolves the piece is a lab job. Get it appraised rather than testing it apart.
Care & handling.
At 5.5 to 6.5 on the Mohs scale it handles careful wear but scratches against quartz and dust. Store it separately and take rings off before rough work.
It breaks with conchoidal fracture, which is worth knowing before you set it or drop it.
Warm water and a soft cloth clean almost everything. Ultrasonic tanks, steamers and household cleaners are where pieces get ruined.
A deeper look.
Extended detail on composition, sourcing, authentication and market value.
The physical record
The formula on record is SiO₂·nH₂O. Crystal system: Amorphous. Specific gravity: 1.9 to 2.3. Streak: White. Cleavage and fracture: Conchoidal fracture.
How it reaches the market
Volcanic opal fields: Querétaro and Jalisco (Mexico, the classics), Ethiopia, Oregon (USA).
What it gets confused with
Carnelian: Carnelian is denser, harder chalcedony with waxy luster; fire opal is lighter and glassier. Orange glass: Glass shows round bubbles and feels warmer than its look. Citrine: Citrine is hard crystal quartz (7); fire opal scratches with a knife edge.
What it is worth
Mid-range; clean red faceted Mexican stones are prized.
Where buyers get caught
Orange glass and resin sell as fire opal online; genuine stone may also craze over years, ask sellers about stability.
One more thing
Aztec nobility treasured fire opal as 'quetzalitzlipyollitli', the stone of the bird of paradise, centuries before European opal fashion.
An education-first guide.
No product links here. We do not sell fire opal, and a guide that only covers our own shelves would not be much of a guide.
Explore the Crystal Guide