Man-made byproduct (often mistaken for Obsidian or Emerald)
Cullet Glass (Industrial Slag Glass)
Amorphous Silica (SiO2) with metallic oxide impurities
Hardness: 5.5-6.5 on Mohs scale; Color: Deep forest green; Luster: Vitreous (glassy); Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Presence of small internal gas bubbles.
- Hardness
- 5
- Color
- Deep forest green
- Luster
- Vitreous (glassy)
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5.5-6.5 on Mohs scale; Color: Deep forest green; Luster: Vitreous (glassy); Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Presence of small internal gas bubbles.
Formation & geological history
Formed as a waste product from glass manufacturing or smelting processes. Molten glass leftovers are dumped and cooled rapidly, creating a glassy, non-crystalline solid. Unlike natural obsidian, it is anthropomorphic in origin.
Uses & applications
Commonly used in landscaping, aquarium decor, or as a source material for decorative glass 'gemstones'. Occasionally used in wire-wrapped jewelry as a simulated forest green obsidian or aventurine.
Geological facts
Green cullet glass is often found near historic glass factory sites. Because it exhibits the same curved (conchoidal) fractures as obsidian, it is frequently misidentified as volcanic glass or rough emerald by novice collectors.
Field identification & locations
Identify in the field by looking for spherical gas bubbles (not found in natural gems), a very uniform color, and a lack of flow banding or mineral inclusions. Often found in riverbeds near old industrial towns or construction fill.
More like this
Other man-made byproduct (often mistaken for obsidian or emerald) specimens
Cullet Glass (Slag Glass)
Amorphous Silicon Dioxide (Industrial Byproduct)
mineraloid
Slag Glass
Anthropogenic Amorphous Silicon Dioxide
mineral
Green Slag Glass
Amorphous Silica / Glassy Blast Furnace Slag
Mineraloid (Industrial byproduct)
Ferrous Slag
Iron/Steel Slag (Complex Calcium-Alumino-Silicates)
Anthropgenic (Industrial Byproduct)
Green Slag
Anthropogenic Silicate Glass
Mineraloid (Industrial byproduct)
Ferrosilicon Slag (Industrial Vitrified Glass)
Vitreous Silicate Residue
Antropogenic (Man-made industrial byproduct)