mineral

Herkimer Diamond

Quartz (Silicon Dioxide, SiO2)

Hardness of 7 on the Mohs scale, colorless or clear (water-clear), vitreous to adamantine luster, trigonal crystal system with double termination (six-sided points on both ends), no cleavage, specific gravity of 2.65.

Identified July 31, 2026More mineral →

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Physical properties

Formation & geological history

Formed in exposed outcrops of the Cambro-Ordovician Little Falls Dolostone in Herkimer County, New York, and surrounding areas. These exceptionally clear crystals grew within cavities (vugs) in the dolostone rock through precipitation from silica-rich solutions over 500 million years ago.

Uses & applications

Popular as collector's specimens, in jewelry making as loose gemstones or wire-wrapped pendants, and in metaphysical practices.

Geological facts

Despite being called 'diamonds' due to their natural sparkle and double-terminated crystal geometry, they are actually exceptionally clear quartz crystals. They are famous for often having up to 18 crystal faces and occasionally containing inclusions of anthracite coal, water, or air bubbles.

Field identification & locations

Found primarily in Herkimer County, New York. They can be identified in the field by their distinct double-terminated hexagonal shape, lack of attached matrix (as they formed freely inside pockets of rock), and exceptional clarity.