Comparison · Quartz Family vs Igneous Rocks
Quartz vs Tuff
Quartz and Tuff are easy to confuse. Quartz is harder (Mohs 7) than Tuff (Mohs 2–5), so Quartz will scratch Tuff 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 Quartz and Tuff
- Quartz is harder (Mohs 7) than Tuff (Mohs 2–5), so Quartz will scratch Tuff and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
- Quartz feels noticeably heavier for its size (specific gravity 2.65 versus 1.5–2.7 for Tuff).
- Hold a thin edge to the light: Quartz is Transparent to translucent, Tuff is Opaque.
- They overlap in pink, gray, and brown, but Quartz also comes in clear, purple, yellow, and black and Tuff also comes in green and white.
Quartz vs Tuff properties
| Property | Quartz | Tuff |
|---|---|---|
| Type | Quartz Family | Igneous Rocks |
| Mohs hardness | 7 | 2–5 |
| Luster | Vitreous, greasy on fracture surfaces | Dull to earthy; glassy shards may show vitreous luster |
| Streak | White | — |
| Transparency | Transparent to translucent | Opaque |
| Specific gravity | 2.65 | 1.5–2.7 |
| Crystal system | Trigonal | — |
| Common colors | Colorless, White, Purple (amethyst), Yellow (citrine), Pink (rose), Brown/black (smoky) | Light gray, Tan, Pink, Greenish, White |
| Rarity | common | common |
| Typical specimen value | $5–$250+ | $1–$75+ |
Which is more valuable?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $10 for Tuff, and premium Quartz can reach $250 or more.
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.
About Tuff
Tuff is a volcanic rock formed from compacted and cemented volcanic ash ejected during explosive eruptions, distinguishing it from lava-derived rocks like basalt or andesite that solidify directly from molten flow. Its texture ranges from soft and crumbly to dense and welded, depending on how hot the ash was when it settled and how much compaction it underwent afterward. Tuff deposits can blanket enormous areas following a single major eruption, preserving a snapshot of that eruption's ash fall in the rock record.
Quartz vs Tuff FAQ
Is Quartz the same as Tuff?
No. Quartz is a quartz family while Tuff is a igneous rock. Quartz is harder (Mohs 7) than Tuff (Mohs 2–5), so Quartz will scratch Tuff and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
How can you tell Quartz from Tuff?
Quartz is harder (Mohs 7) than Tuff (Mohs 2–5), so Quartz will scratch Tuff and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Quartz feels noticeably heavier for its size (specific gravity 2.65 versus 1.5–2.7 for Tuff). Hold a thin edge to the light: Quartz is Transparent to translucent, Tuff is Opaque.
Which is harder, Quartz or Tuff?
Quartz is harder: Mohs 7 against Mohs 2–5 for Tuff.
Which is more valuable, Quartz or Tuff?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $10 for Tuff, and premium Quartz can reach $250 or more.
