Comparison · Minerals vs Quartz Family
Chromite vs Quartz
Chromite and Quartz are easy to confuse. 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. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Chromite and Quartz
- 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.
- Streak color differs: Chromite leaves a dark brown to black streak on unglazed porcelain, Quartz leaves white.
- Luster is different: Chromite is metallic to submetallic while Quartz is vitreous, greasy on fracture surfaces.
- Chromite feels noticeably heavier for its size (specific gravity 4.5–4.8 versus 2.65 for Quartz).
- Hold a thin edge to the light: Chromite is Opaque, Quartz is Transparent to translucent.
- They overlap in black and brown, but Quartz also comes in clear, purple, yellow, pink, and gray.
- Well-formed crystals give it away: Chromite is Isometric, Quartz is Trigonal.
Chromite vs Quartz properties
| Property | Chromite | Quartz |
|---|---|---|
| Type | Minerals | Quartz Family |
| Mohs hardness | 5.5 | 7 |
| Luster | Metallic to submetallic | Vitreous, greasy on fracture surfaces |
| Streak | Dark brown to black | White |
| Transparency | Opaque | Transparent to translucent |
| Specific gravity | 4.5–4.8 | 2.65 |
| Crystal system | Isometric | Trigonal |
| Common colors | Black, Brownish black | Colorless, White, Purple (amethyst), Yellow (citrine), Pink (rose), Brown/black (smoky) |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $5–$250+ |
Which is more valuable?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $20 for Chromite, and premium Quartz can reach $250 or more.
About Chromite
Chromite is iron chromium oxide, FeCr2O4, a member of the spinel group and the only economically significant ore of chromium. It crystallizes in the cubic system as black to brownish-black grains or octahedral crystals, most often found disseminated through dark, dense mafic and ultramafic rocks. Its formation is closely tied to the early crystallization of magma in large layered igneous intrusions.
About Quartz
Quartz is silicon dioxide, SiO2, one of the most abundant minerals in Earth's continental crust, crystallizing in the trigonal division of the hexagonal crystal system with a hardness of 7 that makes it a standard reference point on the Mohs scale. Its six-sided prismatic crystals, often terminated by pyramidal points, are among the most recognizable crystal shapes in mineralogy. Quartz occurs in nearly every rock type and geologic setting, from granite pegmatites to sedimentary sandstones to hydrothermal veins.
Chromite vs Quartz FAQ
Is Chromite the same as Quartz?
No. Chromite is a mineral while Quartz is a quartz family. 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.
How can you tell Chromite from Quartz?
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. Streak color differs: Chromite leaves a dark brown to black streak on unglazed porcelain, Quartz leaves white. Luster is different: Chromite is metallic to submetallic while Quartz is vitreous, greasy on fracture surfaces.
Which is harder, Chromite or Quartz?
Quartz is harder: Mohs 7 against Mohs 5.5 for Chromite.
Which is more valuable, Chromite or Quartz?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $20 for Chromite, and premium Quartz can reach $250 or more.
