Identification guide · Minerals
How to Identify Chromite
Chromite appears as black to brownish-black grains or, less commonly, octahedral crystals with a submetallic to metallic luster and a dark brown streak, distinguishing it from magnetite's black streak. It is weakly to non-magnetic, unlike strongly magnetic magnetite, which is otherwise its closest look-alike in dark ultramafic rock. Hardness of 5.5, a lack of visible cleavage, and its typical association with olivine and serpentine in dense, dark host rock all help confirm chromite in hand specimen.
Chromite identification checklist
| Color | Black, Brownish black | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Metallic to submetallic | 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 | 5.5 | It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. |
| Streak | Dark brown to black | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | None | |
| Fracture | Uneven to conchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 4.5–4.8 | Very heavy, metallic heft (specific gravity about 4.65). |
| Crystal system | Isometric |
Extra tests for Chromite
Magnet test. Weakly magnetic at most; a strong magnet may respond faintly.
Chromite look-alikes and how to tell them apart
Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Chromite vs Franklinite →
Cassiterite is harder (Mohs 6–7) than Chromite (Mohs 5.5), so Cassiterite will scratch Chromite and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Chromite vs Cassiterite →
Quartz is harder (Mohs 7) than Chromite (Mohs 5.5), so Quartz will scratch Chromite and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Chromite vs Quartz →
Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Chromite identification FAQ
How can you tell if a rock is Chromite?
Check the color (black and brownish black), the metallic to submetallic luster, a Mohs hardness of 5.5 and a dark brown to black streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Chromite?
Chromite has a Mohs hardness of 5.5. 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 Chromite and Franklinite?
Chromite (Mohs 5.5, metallic to submetallic luster) and Franklinite (Mohs 5.5–6.5, metallic to submetallic luster) look alike, but hardness, streak and heft usually separate them. See the full Chromite vs Franklinite comparison for a side-by-side table.
Is Chromite worth anything?
Entry-level Chromite specimens sell for around $2, typical collector pieces about $20, and premium examples $150 or more depending on size, quality and locality.
What color is Chromite?
Chromite is most often black and brownish black. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
