Fire Opal
| Also known as | Opal (Opal family) |
|---|---|
| Colour | Orange, Red, Clear, White, Yellow |
| Mohs hardness | 5.5–6 |
| Lustre | Subvitreous to waxy |
| Streak | White |
| Crystal system | Amorphous |
| Transparency | opaque, translucent, transparent |
| Cleavage | None |
| Fracture | Conchoidal to uneven |
| Chemical formula | Hydrated silica. SiO 2 ·nH 2 O |
| Specific gravity | 2.15 |
What is Fire Opal?
Opal is a hydrated amorphous form of silica (SiO2·nH2O); its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to the amorphous (chemical) physical structure, it is classified as a mineraloid, unlike crystalline forms of silica, which are considered minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt.
How to identify Fire Opal
- Lustre: Subvitreous to waxy.
- Hardness: Mohs 5.5–6 — about as hard as a steel knife.
- Streak: White.
- Habit: Amorphous crystal system.
Fire Opal in different forms
Stones often confused with Fire Opal
Frequently asked questions
How hard is Fire Opal?
Fire Opal is Mohs 5.5–6 on the hardness scale.
What colour is Fire Opal?
Fire Opal is typically orange, red, clear, white, yellow (Colorless, white, yellow, red, orange, green, brown, black, blue, pink).