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Herkimer Diamond

Updated: Jul 4, 2022

Recently back from my short breaks in Thailand, I’m sunk in my early summer lethargy at home, amusing myself by watching movies from Netflix and admiring crystals for hours – I admit I sometimes am the laziest human ever, haha :D……..Today I have a day off to unwind and because of that, I have decided to write about my favorite Herkimer Diamonds from the world-renowned locality of Herkimer County, New York, USA. Trust me, Herkimer Diamonds deserve all the credits in the world, they could be insanely beautiful and very valuable when well crystallized, especially when included with other minerals.

What is Herkimer Diamond?

Herkimer Diamond is a generic name for double-terminated floater Quartz crystals discovered within dolomitic rock in and around Herkimer County in New York. Historically, most of the world’s best Quartz specimens have come from this well known locality which have been popular with collectors for more than 120 years. They must be carefully hand mined because they are usually encased in rock matrix or are completely clay-coated, it does require a lot of hard manual labor to find good examples. This is one of the reasons why Herkimer Diamonds are amongst the most expensive Quartz in the world, and most importantly, due to their highly crystallized quality and exceedingly clear clarity resembling real diamonds. They are usually doubly terminated floater specimens of 18 prism faces as prominent as the pyramidal terminations. Real diamonds are polished to give it a geometrical shape, but Herkimer Diamonds are naturally faceted that began forming 500 million years ago, how amazing they are!

When were Herkimer Diamonds discovered?

The very first Herkimer Diamond was discovered in early 18th century by Albert Taber who owned property nearby the Herkimer Diamond Mines. It was only after late 18th century Herkimer Diamonds became widely recognized when workers discovered these incredible crystals in large quantities in the dolomite outcrops at a construction site in the Mohawk River Valley.

How does double-terminated Herkimer Diamond form?

Double-terminated Quartz crystals (also called DT Quartz) are the rare variety of Quartz. These crystals usually form in free floating pockets of magma chamber that slowly evaporated, leaving perfectly formed crystals with terminations on both ends. The most valuable of all would be clusters of double-terminated Herkimer Diamond from the Herkimer County.

Herkimer Diamond with Inclusions

Herkimer Diamonds, like other Quartz crystals, grow in many environments along with many different minerals – petroleum, limonite, hematite, manganese, goethite, chlorite, clay and sands. It is especially amazing to see these substances that have been enclosed during crystal growth are almost perfectly sealed and preserved for millions of years!

Clay and Liquids Inclusions

The very first batches of Herkimer Diamonds were found with gray to black colored inclusions of clay, sand grains and mica that generally cause the formation of phantoms in the crystals. These minerals, as well as watery solutions and gas bubbles can be enclosed by the growing Quartz crystal, creating a series of liquid-filled internal cavities with an air bubble trapped inside – what is commonly called Enhydro Quartz. Some of the Herkimer Diamonds have a cloudy base because of myriads of small bubbles inclusion, but usually the cavities are microscopically small. The most popular Herkimer Diamonds are those with large fluid channel and contain gas bubble or solid mineral that moves about when the crystal is turned.

Skeletal Quartz

Liquid inclusions are often found in Skeletal Quartz. Skeletal Quartz (also known as Elestial Quartz) is recognized by its unique etchings and internal cavities, the dissolution-growth features resulting from unstable conditions during crystallization. Externally, they are often form with geometric lines, patterns and raised terminations etched into the Quartz surface. Internally, these crystals can contain clay minerals of varied colors and often have a layered or ribbed aspect of cavities when accompanied by carbon dioxide or water. Occasionally these cavities are so pronounced to create a hollow center within the Quartz, giving rise to what is called Fenster Quartz.

Beautiful "windows" of Fenster Herkimer Diamond

Fenster Quartz

Minerals like clay that would otherwise be chemically dissolved when the local conditions change are protected by Quartz crystals when they have been embedded inside. Other partially embedded clay might get dissolved at a later stage and leave pockets and hollows form behind. These Quartz crystals are commonly known as Fenster Quartz – a sub-variety of Elestial Quartz. It gets its name from the complex interior skeletal structure which has created many windows and chambers within the Quartz crystal.

Skeletal Herkimer Diamond – 2022’s New Find!

I have recently acquired a precious batch of Skeletal Herkimer Diamonds from a private location in Herkimer County of New York. These new Skeletal Herkimer Diamonds are highly lustrous, have high transparency and are characterized by a stout characteristic – clay-included, occasionally a more or less smoky or citrine color. They are distinctive in that the crystals are all highly prized floater specimens entirely and individually clay-coated when they were discovered from the pocket, some of them even show Fenster Quartz qualities. These specimens begin to come out in February 2022 and they are by far the best examples of that very rare species ever found anywhere. Just a small batch has made it to my hands and of course, good specimens don’t come cheap, at Heritage 1971’s or anywhere else. This remarkable find will certainly reinforce Herkimer Co’s status as the best locality of doubly terminated floater Quartz in the world.

How did Skeletal Herkimer Diamond form?

These Skeletal Herkimer Diamonds were probably deposited by ascending hydrothermal solutions, and the clay settled down on the growing Quartz crystals from levels nearer the surface. The rare and complex forms shown by the Skeletal Herkimer Diamonds suggest a changing physical environment, and the inclusions of clay, the fluid present in some cavities, and the presence of associated carbonate minerals indicate an origin that soil was not subjected to deep freezing during glacial stages – the Pleistocene.

Herkimer Diamonds are magnificent works of nature, found in sedimentary rock, having a diamond-like geometrical shape and transparency. For me, it is much better to be coolly ensconced in my home office, spending hours to admire these glamorous crystals of all time and counting the days until my next holiday :D

Stay cool this summer!

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