mineral

Herkimer Diamond (Quartz with Carbon Inclusions)

Silicon Dioxide (SiO2) with Anthraxolite inclusions

AI-generated identification · may be incorrect

Hardness: 7.5 on Mohs scale; Color: Clear to smoky with black inclusions; Luster: Vitreous; Crystal structure: Hexagonal (doubly terminated); Cleavage: None; Specific Gravity: 2.65

Hardness: 7
Color: Clear to smoky with black inclusions
Luster: Vitreous

Identified July 13, 2026More mineral →

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Physical properties

Hardness: 7.5 on Mohs scale; Color: Clear to smoky with black inclusions; Luster: Vitreous; Crystal structure: Hexagonal (doubly terminated); Cleavage: None; Specific Gravity: 2.65

Formation & geological history

Formed in ancient shallow seas around 500 million years ago within the Little Falls Dolostone through precipitation from hydrothermal fluids. The black inclusions are typically anthraxolite (calcined coal or decayed organic matter).

Uses & applications

Highly prized by mineral collectors, used in wire-wrap jewelry, and used as 'metaphysical' healing crystals. Industrial quartz uses include electronics and glassmaking.

Geological facts

Despite the name, they are quartz crystals, not diamonds. They were first discovered by Mohawk Indians and early settlers in Herkimer County, New York. They are unique for being naturally doubly terminated (pointed at both ends).

Field identification & locations

Identified by their exceptional clarity and 18-faced crystal habit. Found by cracking open vugs (pockets) in dolostone outcrops. Most authentically sourced from Herkimer County, NY.