Comparison · Minerals
Bismuth vs Covellite
Bismuth and Covellite are easy to confuse because both are minerals. Both sit near Mohs 2–2.5, 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 Bismuth and Covellite
- Both sit near Mohs 2–2.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Bismuth leaves a silvery gray streak on unglazed porcelain, Covellite leaves lead-gray to black.
- Both look metallic, so compare color, tarnish and weight rather than shine.
- Bismuth feels noticeably heavier for its size (specific gravity 9.7–9.8 versus 4.6–4.76 for Covellite).
- They overlap in red, blue, and multicolored, but Bismuth also comes in white, gray, pink, and yellow and Covellite also comes in black and purple.
- Well-formed crystals give it away: Bismuth is Trigonal, Covellite is Hexagonal.
Bismuth vs Covellite properties
| Property | Bismuth | Covellite |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 2–2.5 | 1.5–2 |
| Luster | Metallic | Metallic to submetallic/resinous |
| Streak | Silvery gray | Lead-gray to black |
| Transparency | Opaque | Opaque |
| Specific gravity | 9.7–9.8 | 4.6–4.76 |
| Crystal system | Trigonal | Hexagonal |
| Common colors | Silvery white, Pinkish iridescent tarnish (yellow, red, blue hues) | Indigo blue, Blue-black, Iridescent purple/red tarnish |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $2–$150+ |
Which is more valuable?
Typical specimens of Bismuth and Covellite trade in a similar range, around $20.
About Bismuth
Bismuth is a native element mineral, a brittle, silvery-white metal that develops a strikingly iridescent oxide film in shades of pink, yellow, blue, and green as it tarnishes. It has one of the lowest thermal conductivities of any metal and, unusually for a heavy metal, expands slightly as it solidifies from a melt. Both natural crystals and the far more common laboratory-grown crystals show a distinctive stair-step, hopper-like habit.
About Covellite
Covellite is copper sulfide, CuS, a hexagonal mineral instantly recognizable for its deep indigo-blue color and the flashing, rainbow-like iridescence that appears on its surface as it tarnishes. It forms as a secondary mineral in the supergene enrichment zones of copper sulfide deposits, where descending groundwater alters primary copper minerals. Despite its striking appearance, covellite is quite soft and delicate compared to most sulfide minerals collectors encounter.
Bismuth vs Covellite FAQ
Is Bismuth the same as Covellite?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Both sit near Mohs 2–2.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Bismuth from Covellite?
Both sit near Mohs 2–2.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Bismuth leaves a silvery gray streak on unglazed porcelain, Covellite leaves lead-gray to black. Both look metallic, so compare color, tarnish and weight rather than shine.
Which is harder, Bismuth or Covellite?
Bismuth is harder: Mohs 2–2.5 against Mohs 1.5–2 for Covellite.
Which is more valuable, Bismuth or Covellite?
Typical specimens of Bismuth and Covellite trade in a similar range, around $20.
