man-made glass

Blue Goldstone

Aventurine glass (Synthetic borosilicate glass with cobalt and metallic inclusions)

Hardness: 5.5-6.0 Mohs; Color: Deep midnight blue with sparking silver/blue metallic inclusions; Luster: Vitreous; Crystal Structure: Amorphous (glass); Cleavage: None (conchoidal fracture); Specific Gravity: 2.5

Hardness: 5
Luster: Vitreous

Identified March 28, 2026More man-made glass →

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Physical properties

Formation & geological history

Created in a low-oxygen reducing atmosphere furnace where cobalt is added for the blue color and metallic flakes (often copper or manganese) are suspended in the cooling glass molten. While modern production is commercial, the process dates back to 17th-century Venice.

Uses & applications

Primarily used for jewelry (pendants, beads, rings), decorative figurines, palm stones for meditation, and costume accessories.

Geological facts

Despite its name, Goldstone contains no gold. It is often misidentified as a natural mineral like Lapis Lazuli or Blue Sandstone, but it is a glass. Legend says it was discovered by accident by Italian monks, but the recipe likely originated with the Miotti family of Venice.

Field identification & locations

Identify by its perfectly uniform distribution of 'glitter' flakes which do not occur naturally in this patterns in earth-mined stones. It is not found in nature; it is manufactured in factories. For collectors, it is valued for its 'aventurescence' (shimmering effect).

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