Comparison · Silicate Minerals vs Minerals
Moss Agate vs Onyx
Moss Agate and Onyx are easy to confuse. Both sit near Mohs 6.75, 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 Moss Agate and Onyx
- Both sit near Mohs 6.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Hold a thin edge to the light: Moss Agate is translucent, Onyx is Translucent to opaque.
- They overlap in brown and black, but Moss Agate also comes in clear and green and Onyx also comes in white, multicolored, and red.
- Well-formed crystals give it away: Moss Agate is trigonal, Onyx is Trigonal (cryptocrystalline).
Moss Agate vs Onyx properties
| Property | Moss Agate | Onyx |
|---|---|---|
| Type | Silicate Minerals | Minerals |
| Mohs hardness | 6.75 | 6.5–7 |
| Luster | vitreous | Waxy to vitreous |
| Streak | White | White |
| Transparency | translucent | Translucent to opaque |
| Specific gravity | 2.62 | 2.6–2.65 |
| Crystal system | trigonal | Trigonal (cryptocrystalline) |
| Common colors | Colorless, White, Green, Brown, Black | Black and white banded, Brown and white banded, Red and white banded |
| Rarity | common | common |
| Typical specimen value | $5–$150+ | $2–$150+ |
Which is more valuable?
Moss Agate is usually the more valuable of the two: a typical collector specimen runs about $30 against $20 for Onyx, and premium Moss Agate can reach $150 or more.
About Moss Agate
Moss agate is a translucent chalcedony filled with green, brown, or black mineral inclusions that resemble moss or foliage. Despite the name it contains no organic material, and it is widely cut for jewelry.
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.
Moss Agate vs Onyx FAQ
Is Moss Agate the same as Onyx?
No. Moss Agate is a silicate mineral while Onyx is a mineral. Both sit near Mohs 6.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Moss Agate from Onyx?
Both sit near Mohs 6.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Hold a thin edge to the light: Moss Agate is translucent, Onyx is Translucent to opaque. They overlap in brown and black, but Moss Agate also comes in clear and green and Onyx also comes in white, multicolored, and red.
Which is harder, Moss Agate or Onyx?
They are about equally hard, both near Mohs 6.75.
Which is more valuable, Moss Agate or Onyx?
Moss Agate is usually the more valuable of the two: a typical collector specimen runs about $30 against $20 for Onyx, and premium Moss Agate can reach $150 or more.
