Comparison · Materials vs Quartz Family
Glass vs Quartz
Glass and Quartz are easy to confuse. Quartz is harder (Mohs 7) than Glass (Mohs 5.5), so Quartz will scratch Glass 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 Glass and Quartz
- Quartz is harder (Mohs 7) than Glass (Mohs 5.5), so Quartz will scratch Glass 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: Glass leaves a white to colorless streak on unglazed porcelain, Quartz leaves white.
- Hold a thin edge to the light: Glass is translucent, Quartz is Transparent to translucent.
- They overlap in brown and clear, but Glass also comes in green and blue and Quartz also comes in purple, yellow, pink, black, and gray.
- Well-formed crystals give it away: Glass is amorphous, Quartz is Trigonal.
Glass vs Quartz properties
| Property | Glass | Quartz |
|---|---|---|
| Type | Materials | Quartz Family |
| Mohs hardness | 5.5 | 7 |
| Luster | vitreous | Vitreous, greasy on fracture surfaces |
| Streak | White to colorless | White |
| Transparency | translucent | Transparent to translucent |
| Specific gravity | 2.5 | 2.65 |
| Crystal system | amorphous | Trigonal |
| Common colors | Green, Brown, Clear, Blue, White, Frosted | Colorless, White, Purple (amethyst), Yellow (citrine), Pink (rose), Brown/black (smoky) |
| Rarity | common | common |
| Typical specimen value | $1–$40+ | $5–$250+ |
Which is more valuable?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $5 for Glass, and premium Quartz can reach $250 or more.
About Glass
Glass is a man-made amorphous material. Surf-tumbled sea glass and weathered bottle shards are among the most common glassy finds mistaken for natural minerals.
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.
Glass vs Quartz FAQ
Is Glass the same as Quartz?
No. Glass is a material while Quartz is a quartz family. Quartz is harder (Mohs 7) than Glass (Mohs 5.5), so Quartz will scratch Glass 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 Glass from Quartz?
Quartz is harder (Mohs 7) than Glass (Mohs 5.5), so Quartz will scratch Glass 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: Glass leaves a white to colorless streak on unglazed porcelain, Quartz leaves white. Hold a thin edge to the light: Glass is translucent, Quartz is Transparent to translucent.
Which is harder, Glass or Quartz?
Quartz is harder: Mohs 7 against Mohs 5.5 for Glass.
Which is more valuable, Glass or Quartz?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $5 for Glass, and premium Quartz can reach $250 or more.
