RocksdayGoethite vs Psilomelane
The quickest way to tell Goethite from Psilomelane: Goethite leaves a yellowish brown streak; Psilomelane leaves brown.
An iron oxyhydroxide forming dark bubbly or velvety masses, and the main component of rust.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
A group name for hard, black manganese oxides — including romanechite and hollandite — not a single mineral species.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Quick tests
- Streak (rub on unglazed porcelain): Goethite leaves a yellowish brown streak; Psilomelane leaves brown.
Key differences
- Goethite is browner and has a yellow-brown streak.
Side by side
| Property | Goethite | Psilomelane |
|---|---|---|
| Type | Mineral | Mineraloid |
| Mohs hardness | 5–5.5 | 5–6 |
| Luster | Adamantine to silky | Submetallic to dull |
| Streak | Yellowish brown | Brown |
| Colors | Brown, Black, Yellow | Black, Gray |
| Crystal system / structure | Orthorhombic | Botryoidal mixture of manganese oxides |
| Specific gravity | 3.3–4.3 | 3.7–4.7 |
| Formula | FeO(OH) | — |
| Found in | Pikes Peak, Colorado; Cornwall, England | Romanèche, France; Arizona |
Properties that are the same for both are grayed out.
How to identify goethite
- Black-brown botryoidal masses, often with iridescent tarnish.
- Yellow-brown streak.
- Radiating fibers when broken.
Crystal system: Orthorhombic
Full Goethite guide →How to identify psilomelane
- Black, often grape-like (botryoidal) or massive.
- Brownish-black streak.
- Harder than pyrolusite: a knife may barely scratch it.
Structure: Botryoidal mixture of manganese oxides
Full Psilomelane guide →More comparisons
Frequently asked questions
What is the difference between goethite and psilomelane?
Goethite is a mineral with a Mohs hardness of 5–5.5 and an adamantine to silky luster, usually brown, black or yellow. Psilomelane is a mineraloid with a Mohs hardness of 5–6 and a submetallic to dull luster, usually black or gray.
How can you tell goethite from psilomelane?
Goethite leaves a yellowish brown streak; Psilomelane leaves brown. Goethite is browner and has a yellow-brown streak.
Could you tell them apart from a blurry close-up?
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