Comparison · Igneous Rocks vs Quartz Family
Andesite vs Quartz
Andesite and Quartz are easy to confuse. Quartz is harder (Mohs 7) than Andesite (Mohs 5–6), so Quartz will scratch Andesite 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 Andesite and Quartz
- Quartz is harder (Mohs 7) than Andesite (Mohs 5–6), so Quartz will scratch Andesite 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.
- Hold a thin edge to the light: Andesite is Opaque, Quartz is Transparent to translucent.
- They overlap in gray, brown, and black, but Andesite also comes in green and Quartz also comes in clear, purple, yellow, and pink.
Andesite vs Quartz properties
| Property | Andesite | Quartz |
|---|---|---|
| Type | Igneous Rocks | Quartz Family |
| Mohs hardness | 5–6 | 7 |
| Luster | Dull groundmass with vitreous phenocrysts | Vitreous, greasy on fracture surfaces |
| Streak | — | White |
| Transparency | Opaque | Transparent to translucent |
| Specific gravity | 2.5–2.8 | 2.65 |
| Crystal system | — | Trigonal |
| Common colors | Gray, Dark gray, Greenish gray, Brown, Black | 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 Andesite, and premium Quartz can reach $250 or more.
About Andesite
Andesite is a fine-grained, intermediate volcanic rock formed from lava with a silica content between basalt and rhyolite, typically 57 to 63 percent. It is named for the Andes Mountains, where it makes up much of the volcanic arc, and its groundmass is usually too fine to identify individual minerals without magnification. Andesite forms at convergent plate boundaries where oceanic crust melts beneath continental or island arcs.
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.
Andesite vs Quartz FAQ
Is Andesite the same as Quartz?
No. Andesite is a igneous rock while Quartz is a quartz family. Quartz is harder (Mohs 7) than Andesite (Mohs 5–6), so Quartz will scratch Andesite 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 Andesite from Quartz?
Quartz is harder (Mohs 7) than Andesite (Mohs 5–6), so Quartz will scratch Andesite 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. Hold a thin edge to the light: Andesite is Opaque, Quartz is Transparent to translucent. They overlap in gray, brown, and black, but Andesite also comes in green and Quartz also comes in clear, purple, yellow, and pink.
Which is harder, Andesite or Quartz?
Quartz is harder: Mohs 7 against Mohs 5–6 for Andesite.
Which is more valuable, Andesite or Quartz?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $10 for Andesite, and premium Quartz can reach $250 or more.
