Comparison · Sedimentary Rocks vs Quartz Family
Dolomite vs Quartz
Dolomite and Quartz are easy to confuse. Quartz is harder (Mohs 7) than Dolomite (Mohs 3.5–4), so Quartz will scratch Dolomite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Dolomite and Quartz
- Quartz is harder (Mohs 7) than Dolomite (Mohs 3.5–4), so Quartz will scratch Dolomite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
- Hold a thin edge to the light: Dolomite is Opaque, Quartz is Transparent to translucent.
- They overlap in gray, pink, brown, and yellow, but Dolomite also comes in white and Quartz also comes in clear, purple, and black.
Dolomite vs Quartz properties
| Property | Dolomite | Quartz |
|---|---|---|
| Type | Sedimentary Rocks | Quartz Family |
| Mohs hardness | 3.5–4 | 7 |
| Luster | Vitreous to dull | Vitreous, greasy on fracture surfaces |
| Streak | White | White |
| Transparency | Opaque | Transparent to translucent |
| Specific gravity | 2.8–2.9 | 2.65 |
| Crystal system | — | Trigonal |
| Common colors | White, Gray, Pink, Brown, Yellow | Colorless, White, Purple (amethyst), Yellow (citrine), Pink (rose), Brown/black (smoky) |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $5–$250+ |
Which is more valuable?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $10 for Dolomite, and premium Quartz can reach $250 or more.
About Dolomite
Dolomite refers both to the mineral calcium magnesium carbonate, CaMg(CO3)2, and to dolostone, the sedimentary rock composed largely of that mineral. Dolostone typically forms when magnesium-rich water alters existing limestone after deposition, replacing some of the original calcium with magnesium in a process still actively studied by geologists. The rock is usually pale gray, tan, or pinkish and weathers into rounded, pitted outcrops distinct from sharper limestone cliffs.
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.
Dolomite vs Quartz FAQ
Is Dolomite the same as Quartz?
No. Dolomite is a sedimentary rock while Quartz is a quartz family. Quartz is harder (Mohs 7) than Dolomite (Mohs 3.5–4), so Quartz will scratch Dolomite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
How can you tell Dolomite from Quartz?
Quartz is harder (Mohs 7) than Dolomite (Mohs 3.5–4), so Quartz will scratch Dolomite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Hold a thin edge to the light: Dolomite is Opaque, Quartz is Transparent to translucent. They overlap in gray, pink, brown, and yellow, but Dolomite also comes in white and Quartz also comes in clear, purple, and black.
Which is harder, Dolomite or Quartz?
Quartz is harder: Mohs 7 against Mohs 3.5–4 for Dolomite.
Which is more valuable, Dolomite or Quartz?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $10 for Dolomite, and premium Quartz can reach $250 or more.
