Comparison · Quartz Family vs Minerals
Fire Agate vs Onyx
Fire Agate and Onyx are easy to confuse. Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Fire Agate and Onyx
- Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Luster is different: Fire Agate is waxy while Onyx is waxy to vitreous.
- Hold a thin edge to the light: Fire Agate is translucent, Onyx is Translucent to opaque.
- They overlap in brown, red, and multicolored, but Fire Agate also comes in orange and yellow and Onyx also comes in black and white.
- Well-formed crystals give it away: Fire Agate is hexagonal, Onyx is Trigonal (cryptocrystalline).
Fire Agate vs Onyx properties
| Property | Fire Agate | Onyx |
|---|---|---|
| Type | Quartz Family | Minerals |
| Mohs hardness | 7 | 6.5–7 |
| Luster | waxy | Waxy to vitreous |
| Streak | White | White |
| Transparency | translucent | Translucent to opaque |
| Specific gravity | 2.6 | 2.6–2.65 |
| Crystal system | hexagonal | Trigonal (cryptocrystalline) |
| Common colors | Brown, Orange, Red, Gold, Iridescent | Black and white banded, Brown and white banded, Red and white banded |
| Rarity | uncommon | common |
| Typical specimen value | $15–$1000+ | $2–$150+ |
Which is more valuable?
Fire Agate is usually the more valuable of the two: a typical collector specimen runs about $90 against $20 for Onyx, and premium Fire Agate can reach $1000 or more.
About Fire Agate
Fire Agate is an agate variety with iridescent internal color flashes, usually in warm brown, orange, red, and gold tones.
About Onyx
Onyx is a banded variety of chalcedony, a cryptocrystalline form of quartz, distinguished from agate by its straight, parallel bands rather than agate's characteristically curved layers. Most commercial onyx sold in black and white banded slabs is actually dyed to enhance contrast, since naturally occurring true onyx with strong black-and-white banding is relatively uncommon. Chemically identical to other quartz varieties, onyx owes its distinctive look entirely to microscopic banding formed during slow silica deposition.
Fire Agate vs Onyx FAQ
Is Fire Agate the same as Onyx?
No. Fire Agate is a quartz family while Onyx is a mineral. Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Fire Agate from Onyx?
Both sit near Mohs 7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Luster is different: Fire Agate is waxy while Onyx is waxy to vitreous. Hold a thin edge to the light: Fire Agate is translucent, Onyx is Translucent to opaque.
Which is harder, Fire Agate or Onyx?
They are about equally hard, both near Mohs 7.
Which is more valuable, Fire Agate or Onyx?
Fire Agate is usually the more valuable of the two: a typical collector specimen runs about $90 against $20 for Onyx, and premium Fire Agate can reach $1000 or more.
