man‑made glass (yellow glass/slag)
mineral · common
Quick facts
- Formula
- approx. SiO2 with Na2O, CaO and other modifiers/colorants
- Hardness
- about 5–6 (commonly ~5.5)
- Luster
- vitreous
- Colors
- colorless to any color with additives; here yellow
Glass is an artificial, non-crystalline solid produced by melting silica with fluxes and stabilizers. Decorative tumbled or knapped pieces are common in rock shops and can mimic natural gems by color and luster.
Look for smoothly curved surfaces, gas bubbles, and flow lines, with sharp conchoidal chips and an absence of crystal faces or cleavage.
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Photograph your specimen on arockid.com or in RockSnap / RockID. Three free IDs a day — no card.
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