mineral

Herkimer Diamond

Quartz (Silicon Dioxide, SiO2)

Hardness: 7.5 on Mohs scale (harder than normal quartz); Color: Colorless, clear, or smoky; Luster: Vitreous/Glassy; Crystal Structure: Hexagonal (doubly terminated); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7
Color: Colorless, clear, or smoky
Luster: Vitreous/Glassy

Identified March 21, 2026More mineral →

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Physical properties

Formation & geological history

Formed roughly 500 million years ago within pockets of Little Falls Dolostone during the Cambrian period. They precipitated from hydrothermal fluids in cavities (vugs) lined with drusy quartz.

Uses & applications

Used primarily in jewelry as a substitute for diamonds (due to their clarity and natural facets) and highly valued by mineral collectors for their unique double-termination.

Geological facts

They are not actually diamonds but are called so because of their clarity and natural facet-like shape. They often contain 'anthraxolite' inclusions (black carbon) or water bubbles (enhydros).

Field identification & locations

Identify in the field by looking for double-terminated (pointed at both ends) crystals in vugs of dolostone. Found most famously in Herkimer County, New York, USA. Collectors look for high clarity and lack of chips.