Comparison · Materials
Glass vs Slag Glass
Glass and Slag Glass are easy to confuse because both are materials. Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Glass and Slag Glass
- Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- They overlap in green, brown, and blue, but Glass also comes in clear and Slag Glass also comes in black and white.
Glass vs Slag Glass properties
| Property | Glass | Slag Glass |
|---|---|---|
| Type | Materials | Materials |
| Mohs hardness | 5.5 | 5.5 |
| Luster | vitreous | vitreous |
| Streak | White to colorless | White to colorless |
| Transparency | translucent | translucent |
| Specific gravity | 2.5 | 2.5 |
| Crystal system | amorphous | amorphous |
| Common colors | Green, Brown, Clear, Blue, White, Frosted | Blue, Green, Black, Brown, White, Swirled |
| Rarity | common | common |
| Typical specimen value | $1–$40+ | $1–$80+ |
Which is more valuable?
Slag Glass is usually the more valuable of the two: a typical collector specimen runs about $10 against $5 for Glass, and premium Slag Glass can reach $80 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 Slag Glass
Slag Glass is glassy industrial byproduct or manufactured glass with swirled colors, sometimes collected or knapped like stone.
Glass vs Slag Glass FAQ
Is Glass the same as Slag Glass?
No. Both are materials, but they are distinct species with different hardness, streak or luster. Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Glass from Slag Glass?
Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. They overlap in green, brown, and blue, but Glass also comes in clear and Slag Glass also comes in black and white.
Which is harder, Glass or Slag Glass?
They are about equally hard, both near Mohs 5.5.
Which is more valuable, Glass or Slag Glass?
Slag Glass is usually the more valuable of the two: a typical collector specimen runs about $10 against $5 for Glass, and premium Slag Glass can reach $80 or more.
