Identification guide · Sulfide Minerals
How to Identify Marcasite
Marcasite is usually pale brass yellow, tin white, and bronze with a metallic luster and is opaque. It has a Mohs hardness of 6. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Its streak is dark greenish gray to brownish black. It is most often confused with Pyrite, Arsenopyrite, and Dolomite; the tests below separate them.
Marcasite identification checklist
| Color | Pale brass yellow, Tin white, Bronze | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Metallic | Turn it under a lamp: a true metallic shine reflects like polished metal and stays opaque at thin edges. |
| Transparency | Opaque | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 6 | It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. |
| Streak | Dark greenish gray to brownish black | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Distinct on {101} | |
| Fracture | Uneven | |
| Specific gravity | 4.9 | Very heavy, metallic heft (specific gravity about 4.9). |
| Crystal system | Orthorhombic |
Marcasite look-alikes and how to tell them apart
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Marcasite vs Pyrite →
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Marcasite vs Arsenopyrite →
Marcasite is harder (Mohs 6) than Dolomite (Mohs 3.5–4), so Marcasite will scratch Dolomite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Marcasite vs Dolomite →
Marcasite is harder (Mohs 6) than Sphalerite (Mohs 3.75), so Marcasite will scratch Sphalerite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
Field tips
- Look for pale brass-yellow color, often lighter than pyrite, in cockscomb or spear-shaped twinned crystals.
- Marcasite is brittle and tends to tarnish, crumble, and develop white sulfate crusts as it ages.
- Distinguish it from pyrite by crystal habit, paler color, and its tendency to decay in storage.
Marcasite identification FAQ
How can you tell if a rock is Marcasite?
Check the color (pale brass yellow, tin white, and bronze), the metallic luster, a Mohs hardness of 6 and a dark greenish gray to brownish black streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Marcasite?
Marcasite has a Mohs hardness of 6. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
What is the difference between Marcasite and Pyrite?
Marcasite (Mohs 6, metallic luster) and Pyrite (Mohs 6.5, metallic luster) look alike, but hardness, streak and heft usually separate them. See the full Marcasite vs Pyrite comparison for a side-by-side table.
Is Marcasite worth anything?
Entry-level Marcasite specimens sell for around $5, typical collector pieces about $35, and premium examples $200 or more depending on size, quality and locality.
What color is Marcasite?
Marcasite is most often pale brass yellow, tin white, and bronze. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
