Comparison · Materials
Opalite vs Slag Glass
Opalite 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 Opalite 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 white and blue, but Opalite also comes in yellow and Slag Glass also comes in green, black, and brown.
Opalite vs Slag Glass properties
| Property | Opalite | 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 | 2.4 | 2.5 |
| Crystal system | amorphous | amorphous |
| Common colors | Milky White, Blue, Yellow, Opalescent | Blue, Green, Black, Brown, White, Swirled |
| Rarity | common | common |
| Typical specimen value | $3–$70+ | $1–$80+ |
Which is more valuable?
Opalite is usually the more valuable of the two: a typical collector specimen runs about $15 against $10 for Slag Glass, and premium Opalite can reach $70 or more.
About Opalite
Opalite is a retail trade name for manmade opalescent glass and related opal simulants, commonly sold as tumbled stones or jewelry.
About Slag Glass
Slag Glass is glassy industrial byproduct or manufactured glass with swirled colors, sometimes collected or knapped like stone.
Opalite vs Slag Glass FAQ
Is Opalite 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 Opalite 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 white and blue, but Opalite also comes in yellow and Slag Glass also comes in green, black, and brown.
Which is harder, Opalite or Slag Glass?
They are about equally hard, both near Mohs 5.5.
Which is more valuable, Opalite or Slag Glass?
Opalite is usually the more valuable of the two: a typical collector specimen runs about $15 against $10 for Slag Glass, and premium Opalite can reach $70 or more.
