mineral
Cobalt Blue Glass / Cullet Glass
Silicon dioxide (Amorphous man-made glass)
Hardness of 5.5 on the Mohs scale, vibrant royal blue color, vitreous luster, amorphous crystal structure (no cleavage, conchoidal fracture), specific gravity around 2.4 - 2.8.
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Physical properties
Hardness of 5.5 on the Mohs scale, vibrant royal blue color, vitreous luster, amorphous crystal structure (no cleavage, conchoidal fracture), specific gravity around 2.4 - 2.8.
Formation & geological history
Man-made industrial byproduct or decorative glass cullet, formed by rapid cooling of molten silicate materials mixed with metal oxides like cobalt.
Uses & applications
Often sold mistakenly or deceptively as high-end raw sapphire, tanzanite, or lapis lazuli to novice collectors; used in decorative glass art, landscaping, and industrial glass manufacturing.
Geological facts
This specimen is frequently misrepresented in online marketplaces as a massive, multi-thousand-dollar raw sapphire or high-grade gem rough. True sapphire of this size and color would be extremely rare and valuable, whereas cullet glass has minimal commercial value.
Field identification & locations
Easily identified in the field or by collectors due to the presence of internal spherical air bubbles, perfectly smooth conchoidal fracture surfaces, and a lack of natural crystal growth striations.
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