mineral

Herkimer Diamond

Quartz (Silicon Dioxide - SiO2)

Hardness: 7.5 on the Mohs scale. Color: Colorless to water-clear with occasional black anthraxolite inclusions. Luster: Adamantine to vitreous. Crystal structure: Hexagonal/trigonal with naturally occurring double terminations (18 total facets). Cleavage: None. Specific gravity: 2.65.

Hardness: 7
Luster: Adamantine to vitreous

Identified July 22, 2026More mineral →

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Physical properties

Formation & geological history

Formed during the Cambrian Period approximately 500 million years ago in shallow, warm sea environments within dolostone host rock (Little Falls Formation). Cavities (vugs) formed, allowing slow crystallization of silica-rich solutions.

Uses & applications

Popular among gem collectors, mineral enthusiasts, and used extensively in jewelry, wire-wrapping, and metaphysical applications due to high natural clarity and brilliance.

Geological facts

Herkimer Diamonds are not true diamonds; they are doubly terminated quartz crystals. True diamonds are carbon-based with a hardness of 10, whereas Herkimers are silica-based with a hardness of 7.5. They are uniquely naturally faceted with 18 distinct faces (six faces at each point and six around the middle).

Field identification & locations

Identified by their exceptional clarity, natural double terminations, and characteristic geometry. Primarily found in Herkimer County, New York, USA. Collectors hunt for them by breaking open vugs in hard vuggy dolostone rock using sledgehammers and chisels.