Herkimer Diamonds, often resembling true diamonds, are captivating due to their unique appearance. Despite their name, these stunning crystals are not true diamonds but a prized variety of quartz. Their formation and characteristics set them apart in the world of minerals, making them of interest to enthusiasts and collectors.
What is a Herkimer Diamond?
A Herkimer Diamond is a naturally occurring, double-terminated quartz crystal. Unlike most quartz, Herkimer Diamonds feature natural facets at both ends, giving them a distinct symmetrical shape. Composed of silicon dioxide (SiO2), they differ chemically from true diamonds, which are carbon-based.
They are characterized by exceptional clarity and often brilliant, glassy luster. Many specimens are hexagonal with 18 natural facets, contributing to their diamond-like appeal. While typically colorless and transparent, some may contain inclusions like hydrocarbon deposits, air bubbles, or small phantom crystals. They range in size from tiny fragments to several inches; larger, flawless specimens are particularly valued.
Where Do They Come From?
Herkimer Diamonds are primarily found in Herkimer County, New York, and the surrounding Mohawk River Valley, from which they derive their name. Their formation began approximately 500 million years ago within Cambrian-age dolostone bedrock, specifically the Little Falls Formation, which formed from ancient marine sediments.
Acidic waters created cavities, known as vugs, within this dolostone, which became growth chambers for the quartz crystals. Silica-rich fluids permeated these vugs, allowing crystals to grow freely without attachment to a host rock, enabling their characteristic double-terminated shape. Growth within confined spaces contributed to their clarity and well-defined forms. The discovery of these crystals dates back to the late 18th century when workmen in the region first unearthed them.
Why Are They So Special?
Herkimer Diamonds are special due to several unique attributes. Their exceptional, often gem-quality, clarity allows light to pass through, creating notable brilliance. This transparency and natural faceting give them a striking resemblance to cut diamonds.
Their natural double termination, with pointed facets at both ends, is a rare characteristic for quartz crystals. They possess a hardness of 7.5 on the Mohs scale, making them durable for jewelry and other applications without extensive cutting or polishing. These properties make them highly sought after by collectors, jewelers, and those interested in metaphysical associations.