Comparison · Igneous Rocks vs Quartz Family
Porphyry vs Quartz
Porphyry and Quartz are easy to confuse. Quartz is harder (Mohs 7) than Porphyry (Mohs 5–7), so Quartz will scratch Porphyry 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 Porphyry and Quartz
- Quartz is harder (Mohs 7) than Porphyry (Mohs 5–7), so Quartz will scratch Porphyry 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: Porphyry is Opaque, Quartz is Transparent to translucent.
- They overlap in purple and gray, but Porphyry also comes in red and green and Quartz also comes in clear, yellow, pink, black, and brown.
Porphyry vs Quartz properties
| Property | Porphyry | Quartz |
|---|---|---|
| Type | Igneous Rocks | Quartz Family |
| Mohs hardness | 5–7 | 7 |
| Luster | Dull to vitreous | Vitreous, greasy on fracture surfaces |
| Streak | — | White |
| Transparency | Opaque | Transparent to translucent |
| Specific gravity | 2.6–2.8 | 2.65 |
| Crystal system | — | Trigonal |
| Common colors | Purple, Red, Gray, Green | 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 Porphyry, and premium Quartz can reach $250 or more.
About Porphyry
Porphyry is a textural term for any igneous rock that contains large, visible crystals called phenocrysts embedded in a much finer-grained groundmass, rather than a description of a specific mineral composition. The texture records a two-stage cooling history, slow crystal growth at depth followed by rapid cooling near or at the surface. Porphyry can be volcanic or shallow intrusive and of almost any composition, from basaltic to rhyolitic.
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.
Porphyry vs Quartz FAQ
Is Porphyry the same as Quartz?
No. Porphyry is a igneous rock while Quartz is a quartz family. Quartz is harder (Mohs 7) than Porphyry (Mohs 5–7), so Quartz will scratch Porphyry 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 Porphyry from Quartz?
Quartz is harder (Mohs 7) than Porphyry (Mohs 5–7), so Quartz will scratch Porphyry 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: Porphyry is Opaque, Quartz is Transparent to translucent. They overlap in purple and gray, but Porphyry also comes in red and green and Quartz also comes in clear, yellow, pink, black, and brown.
Which is harder, Porphyry or Quartz?
Quartz is harder: Mohs 7 against Mohs 5–7 for Porphyry.
Which is more valuable, Porphyry or Quartz?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $10 for Porphyry, and premium Quartz can reach $250 or more.
