Herkimer "Diamond"

Trade name for double-terminated quartz crystals firstly found in the late 18th century at Little Falls in Herkimer County, New York.

Origin of name: after the locality

Synonyms and trade names: Little Falls Diamond, Middleville Diamond

Can be confused with: Due to their outstanding beauty and appearance, Herkimer "Diamonds" can hardly be confused with rock crystals from other localities

Localities: Herkimer, Fulton and Montgomery Counties, New York, USA



Interesting facts: Herkimer "Diamonds" are found as doubly-terminated crystals, characterized by outstanding clarity and luster. The formation of Herkimer "Diamonds" is not fully unravelled yet. Geologists and mineralogists theorize, that they are of hydrothermal origin i.e. the crystallized from water or watery solutions entrapped in small cavities in the host rock. Formation temperatures may have been as low as 200°C and crystal growth extremely slow, which could explain the remarkable clarity and luster.



Herkimer Diamonds are also known for their spectacular inclusions, e.g. phantom crystals, skeleton crystals, hydrocarbons (oil) and fluid inclusions which in rare cases can be two-phase (fluid and gas) or even three-phase (fluid, gas and crystal).


Herkimer "Diamonds" with oil- (hydrocarbon-) inclusions

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