Slag Glass
Slag Glass is glassy industrial byproduct or manufactured glass with swirled colors, sometimes collected or knapped like stone.
Slag Glass properties at a glance
| Type | Materials |
|---|---|
| Chemical formula | Industrial silicate glass |
| Mohs hardness | 5.5 |
| Crystal system | amorphous |
| Luster | vitreous |
| Streak | White to colorless |
| Cleavage | None |
| Fracture | Conchoidal |
| Specific gravity | 2.5 |
| Transparency | translucent |
| Common colors | Blue, Green, Black, Brown, White, Swirled |
| Rarity | common |
Geology & background
Forms as glassy industrial byproduct from furnaces, smelting, or glass manufacturing rather than natural geological crystallization.
Slag Glass is associated with industrial glassmaking, metal smelting, and decorative glass traditions.
How to identify Slag Glass
- Look for bubbles, flow bands, glassy fracture, and unnatural color swirls.
- Industrial context or sharp glassy chips strongly supports slag glass.
- Compare against natural Obsidian, Chert, and Agate before assigning a geological name.
Where Slag Glass is found
Slag Glass is a retail or manufactured material label; record seller disclosure and provenance when known.
How much is Slag Glass worth?
| Entry-level specimen | $1 |
|---|---|
| Typical collector specimen | $10 |
| Premium specimen | $80+ |
Value is usually decorative or lapidary-market value, not natural rarity. Price depends on size, polish, color effect, condition, seller disclosure, and craftsmanship.
Common uses
- Decorative objects
- Lapidary practice
- Knapped art
- Historic industrial collecting
Interesting facts
- Some slag glass resembles obsidian, chert, or colorful agate at first glance.
- It may contain bubbles, flow lines, or industrial colorants.
- Historic slag pieces can be collectible, but the material is not a natural mineral.
Care & safety
Slag Glass may be glass, coated, dyed, or otherwise manufactured; handle it as a decorative material unless verified otherwise.
Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a properly rated respirator.
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