VarietyA variety of Quartz
Herkimer diamond
SiO₂Herkimer elması
Water-clear quartz crystals pointed at both ends: called “diamonds”, they are quartz grown in the dolomite rocks of New York State.
Also known as: Middleville diamond · Little Falls diamond
- Popularly: Semi-precious stone
In short
Herkimer diamond is the trade name for very clear quartz crystals pointed at both ends (doubly terminated) that are found in dolomite outcrops in and around Herkimer County and the Mohawk River Valley in New York State, USA. They are not diamonds; the name comes from their clarity and their well-formed, shiny crystal faces. Because the first finds were made in the village of Middleville and the city of Little Falls, they are also called “Middleville diamonds” or “Little Falls diamonds”.
Photos
How does it form?
The story of Herkimer diamonds begins about 500 million years ago, in the Cambrian period. At that time a shallow sea covered the area, receiving calcium and magnesium carbonate sediments worn from the ancient Adirondack Mountains to the north. These sediments hardened into the dolomite rock now called the Little Falls Formation. While the rock was buried, acidic water passing through it opened small cavities (vugs).
The quartz crystals in these cavities are thought to have grown much later, in the Carboniferous period. Hot, silica-rich water was trapped in the cavities, and quartz crystallised from it very slowly, perhaps at temperatures as low as 200 °C. Because the crystals grew with almost no contact with the rock, as if suspended in the fluid, points developed at both ends; this is uncommon in quartz. The slow growth may also explain their remarkable clarity and lustre. The cavity walls are often lined with tiny quartz crystals and coated with a tarry hydrocarbon.
What is it used for?
- Collecting: displayed in their natural state, they are among the quartz specimens collectors love most.
- Jewellery: they are often used uncut, with their natural faces, drilled or wire-wrapped in necklaces, earrings and rings.
- Outings and hobby: the fee-digging mines of New York draw many visitors every summer to hunt for their own crystals.
- History: the Mohawk people used the crystals as amulets and for making tools, and valued them as trade goods.
Where is it found?
Herkimer diamonds are found in Herkimer, Fulton and Montgomery counties in New York State. The best-known digging sites lie near Middleville, along State Routes 28 and 29: they include Ace of Diamonds, Herkimer Diamond Mines and Crystal Grove near St. Johnsville. There is also fee digging on private land near Fonda.
Similar crystals exist elsewhere in the world; the “Maramureș diamonds” of the Ukrainian Carpathians are one example. The Cape May diamonds of the United States are another kind of quartz called “diamonds”. For quartz in general, see the quartz page, and for clear quartz the rock crystal page.
What determines its value?
The value of a Herkimer diamond depends mostly on its clarity, brilliance, size, and on both points being undamaged and well formed. Water-clear crystals with flawless points, and those with interesting inclusions such as moving bubbles, phantom crystals or black hydrocarbon, are sought by collectors. Crystals documented as coming from Herkimer attract more interest than similar ones from elsewhere. As quartz, it has no value comparable to a real diamond.
This information is educational, not buying, selling or investment advice. Value varies enormously with quality and treatment.
How to recognise it
- 1
Both ends of the crystal finish in a six-sided point; most crystals are short and stubby, from a few millimetres to more than 20 centimetres long.
- 2
They are usually water-clear and colourless, sometimes smoky; their faces are naturally glassy and bright.
- 3
Inside you may see specks of black hydrocarbon (a tar-like carbon material) or fluid inclusions holding salt water, petroleum and gas bubbles.
- 4
Its hardness is 7: it scratches glass, but a real diamond, with a hardness of 10, scratches it easily.
Fakes and imitations
What shops usually don’t tell you:
- Similar doubly terminated quartz crystals from other parts of the world are often sold as “Herkimer”. They may look the same, but since they do not come from New York they do not rightly carry the name; ask where the stone comes from.
Myths and misconceptions
MythHerkimer diamonds are real diamonds.
FactHerkimer diamonds are quartz; the word “diamond” comes only from their clarity and well-formed crystal faces. Their hardness is 7, while diamond's is 10.
MythAny clear quartz crystal with two points is a Herkimer diamond.
FactSimilar doubly terminated crystals occur in many places, including Afghanistan, Arizona, Norway, Ukraine and China, and are often sold as “Herkimer”; but the name rightly belongs only to crystals from the Herkimer area of New York.
What is it believed to be good for?
This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.
The meanings people give this stone, and who holds them:
- The Mohawk people and early settlers are known to have carried the crystals as amulets.
- Today crystal-therapy websites present the Herkimer diamond as a “stone of attunement” and claim that it clears the mind and supports spiritual growth.
- The same sources claim that the stone stimulates the immune system.
What science says
A Herkimer diamond is the same mineral as any other quartz crystal; there is no scientific evidence that it clears the mind, has a spiritual effect or stimulates the immune system. Problems with the immune system call for a doctor.
Did you know?
The Mohawk people and early settlers found the crystals in stream sediments and ploughed fields, used them to make tools and traded them with other tribes; interest faded when European glass beads arrived in the early 1600s.
The crystals became widely known in the late 18th century, when workmen cutting into the Mohawk Valley dolomite came across them in large numbers.
The fluid droplets in some crystals hold a gas bubble, and rarely a third phase; they are tiny samples of the fluid in which the crystal grew.
Today the mines around Middleville let anyone dig for their own crystals for a small fee.
Where is it found?
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- Middleville, Herkimer County, New York, USA · Type localityOne of the first discovery sites (“Middleville diamond”); today fee-digging mines such as Ace of Diamonds and Herkimer Diamond Mines lie along New York State Routes 28 and 29
- Little Falls, Herkimer County, New York, USA · Historic sourceOne of the places where the crystals were first found in the late 18th century; the host rock, the Little Falls Formation, is named after the town
- St. Johnsville area, Montgomery County, New York, USA · Known localityAt the Crystal Grove Diamond Mine, visitors can dig by hand in the Little Falls dolostone
- Fonda area, Montgomery County, New York, USA · Known localityFee digging on private land known as Hastings Farm or Diamond Acres
Locations are approximate to protect sites. Red dots mark places in Türkiye. Open in the big map →
Frequently asked questions
What is Herkimer diamond?
Herkimer diamond is the trade name for very clear quartz crystals pointed at both ends (doubly terminated) that are found in dolomite outcrops in and around Herkimer County and the Mohawk River Valley in New York State, USA. They are not diamonds; the name comes from their clarity and their well-formed, shiny crystal faces. Because the first finds were made in the village of Middleville and the city of Little Falls, they are also called “Middleville diamonds” or “Little Falls diamonds”.
What is Herkimer diamond used for?
Collecting: displayed in their natural state, they are among the quartz specimens collectors love most. Jewellery: they are often used uncut, with their natural faces, drilled or wire-wrapped in necklaces, earrings and rings. Outings and hobby: the fee-digging mines of New York draw many visitors every summer to hunt for their own crystals. History: the Mohawk people used the crystals as amulets and for making tools, and valued them as trade goods.
How hard is Herkimer diamond?
It has a hardness of 7 on the Mohs scale. It scratches glass and steel; a steel knife cannot scratch it. Its specific gravity is 2.65–2.66 g/cm³.
Where is Herkimer diamond found?
Its best-known localities: Middleville, Herkimer County, New York, USA; Little Falls, Herkimer County, New York, USA; St. Johnsville area, Montgomery County, New York, USA; Fonda area, Montgomery County, New York, USA.
How can you tell if Herkimer diamond is real?
Both ends of the crystal finish in a six-sided point; most crystals are short and stubby, from a few millimetres to more than 20 centimetres long. They are usually water-clear and colourless, sometimes smoky; their faces are naturally glassy and bright. Inside you may see specks of black hydrocarbon (a tar-like carbon material) or fluid inclusions holding salt water, petroleum and gas bubbles. Similar doubly terminated quartz crystals from other parts of the world are often sold as “Herkimer”. They may look the same, but since they do not come from New York they do not rightly carry the name; ask where the stone comes from.
Is Herkimer diamond valuable?
On the “street to diamond” value ladder it sits on step 5 of nine: Ornamental stone. The value of a Herkimer diamond depends mostly on its clarity, brilliance, size, and on both points being undamaged and well formed. Water-clear crystals with flawless points, and those with interesting inclusions such as moving bubbles, phantom crystals or black hydrocarbon, are sought by collectors. Crystals documented as coming from Herkimer attract more interest than similar ones from elsewhere. As quartz, it has no value comparable to a real diamond.
What is Herkimer diamond good for?
The Mohawk people and early settlers are known to have carried the crystals as amulets. Today crystal-therapy websites present the Herkimer diamond as a “stone of attunement” and claim that it clears the mind and supports spiritual growth. The same sources claim that the stone stimulates the immune system. A Herkimer diamond is the same mineral as any other quartz crystal; there is no scientific evidence that it clears the mind, has a spiritual effect or stimulates the immune system. Problems with the immune system call for a doctor. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.
Family
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Sources
- Herkimer diamond · Wikipedia
- Herkimer Diamonds · Geology.com
- Herkimer “Diamond” · Vienna Gem Center (edelsteine.at), Gemstone lexicon
- Herkimer Diamonds in Spades (J. Landon) · Rock & Gem Magazine, 2012
- Herkimer Diamond · Minerals.net
- Quartz (“Herkimer Diamond”) (near Herkimer, New York State, USA) 5 (J. St. John) · Wikimedia Commons
- Middleville, New York · Wikipedia
- Little Falls, New York · Wikipedia
- St. Johnsville (village), New York · Wikipedia
- Fonda, New York · Wikipedia
External links
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