Comparison · Minerals
Cassiterite vs Onyx
Cassiterite and Onyx are easy to confuse because both are minerals. Both sit near Mohs 6–7, 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 Cassiterite and Onyx
- Both sit near Mohs 6–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Cassiterite leaves a white to grayish brown streak on unglazed porcelain, Onyx leaves white.
- Luster is different: Cassiterite is adamantine to submetallic while Onyx is waxy to vitreous.
- Cassiterite feels noticeably heavier for its size (specific gravity 6.8–7.1 versus 2.6–2.65 for Onyx).
- They overlap in brown, black, and red, but Cassiterite also comes in yellow and gray and Onyx also comes in white and multicolored.
- Well-formed crystals give it away: Cassiterite is Tetragonal, Onyx is Trigonal (cryptocrystalline).
Cassiterite vs Onyx properties
| Property | Cassiterite | Onyx |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 6–7 | 6.5–7 |
| Luster | Adamantine to submetallic | Waxy to vitreous |
| Streak | White to grayish brown | White |
| Transparency | Translucent to opaque | Translucent to opaque |
| Specific gravity | 6.8–7.1 | 2.6–2.65 |
| Crystal system | Tetragonal | Trigonal (cryptocrystalline) |
| Common colors | Brown, Black, Reddish brown, Yellow, Gray | Black and white banded, Brown and white banded, Red and white banded |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $2–$150+ |
Which is more valuable?
Typical specimens of Cassiterite and Onyx trade in a similar range, around $20.
About Cassiterite
Cassiterite is tin oxide, SnO2, and has been the principal ore of tin since the Bronze Age. It crystallizes in the tetragonal system, typically as reddish-brown to black prismatic or pyramidal crystals with an adamantine luster and exceptionally high density for a nonmetallic-looking mineral. Its resistance to weathering means it survives erosion intact and concentrates in stream gravels as placer tin.
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.
Cassiterite vs Onyx FAQ
Is Cassiterite the same as Onyx?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Both sit near Mohs 6–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Cassiterite from Onyx?
Both sit near Mohs 6–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Cassiterite leaves a white to grayish brown streak on unglazed porcelain, Onyx leaves white. Luster is different: Cassiterite is adamantine to submetallic while Onyx is waxy to vitreous.
Which is harder, Cassiterite or Onyx?
They are about equally hard, both near Mohs 6–7.
Which is more valuable, Cassiterite or Onyx?
Typical specimens of Cassiterite and Onyx trade in a similar range, around $20.
