Herkimer Diamonds

Herkimer Diamonds are found in upstate New York. These exceptionally clear quartz crystals are double terminated and require very little cleaning as they are naturally faceted. Herkimer Diamonds do require a great deal of work to retrieve. The dolostone they are found in is extremely hard and although it can be broken with a crack hammer more modern tools are better suited.

Watch our video of the "The best Herkimer Diamond" Find Ever!

Herkimer Diamond Mining Tips & Tools

Be prepared to have essential tools & tips ready for your rockhounding trip. Necessary tools for rockhounding include: a good Estwing crack hammer, small chisels, wedges, buckets, and a wire screen. Basic Tips include: Bring plenty of mosquito repellent, snacks & water, ear & eye protection, gloves, and check the Weather! A small 1200+ watt generator and power breaker will greatly increase your odds of finding large Herkimer Diamond pockets. A 4-6 foot long pry bar is also a great tool to have handy when trying to leverage against large stubborn rocks. For the more serious miner, a 65lb Jackhammer which can be rented at local hardware stores. "Professionals" often use set up water pumps during the rainy mining season and also as the escavation depth gets closer to the water table. Local miners will often trade lesser findings with a bit of friendly talk and easily show off their best finds of the day. Mining is hard work, be prepared for 3-4 hrs of serious rockhounding. Enjoy!

Are all Herkimer Diamonds double-terminated quartz crystals? The answer is yes. Does that make all double-terminated quartz crystals Herkimer diamonds then? The answer is no.Herkimer refers to the location of these unusual quartz clusters found in hollow "pockets". Herkimer County is about a 4 and a half hours drive north of New York City. The name Herkimer comes from an American Revolution General named Nicholas Herkimer who died in battle in 1777.

Watch our video of a Giant Rainbow Herkimer Diamond Discovery

Herkimer Diamond Terminology

  • Opaque: Cloudy and milky, light does not pass through.
    • Often caused by mining fracturing.
  • Translucent: Clear light does pass through.
    • Etymology is Latin Trans meaning through or passing through and Lucent meaning glow or light.
  • Value: Desirable Herkimer Diamonds are translucent and unfractured allowing light to cleary pass through.
    • Some rare varieties include rainbows and smoky colors.
  • Hardness: Herkimer Diamonds are Quartz.
    • Mohs Scale Hardness = 6. Between Topaz (harder) and Feldspar (softer).

Herkimer Diamond Formation

Now the source and formation of Herkimer Diamonds is of particular interest to us here at American Geode because the Herkimer Diamond was formed in "pockets" not unlike the pockets that formed geodes. Most quartz crystals grow, over the course of millions of years attached to a matrix, attached to the surrounding rock or stone. So in those formations only one end of the quartz crystal grows to its point. With Herkimer Diamonds forming inside pockets, freed from the surrounding matrix stone, they grow points on both ends.

The Herkimer Diamond began forming nearly 500 million years ago in pockets within a sedimentary rock called Dolostone (Dolomite and Limestone). Sedimentary rock, different from its two cousins Igneous rock and Metamorphic rock, is formed by layers of mineral and organic matter under hundreds of million years of pressure. As more layers of mineral and organic matter are deposited, this increases the pressure and weight on the lower and earlier layers of sedimentary rock below. The Dolostone covered Herkimer County during the Cambrian Age, when Herkimer County was also the bottom of the sea that spanned across North America.

Now this is the part of the Herkimer Diamond formation that is similar to the way geodes are formed: organic material, plants and sea life would die and be buried under new layers of sedimentary stone. When these plants and other sea life would decompose under the rock, they release gases, and this gas is what formed the "pocket." Evidence of this organic, plant material succumbing to decomposition is clear when you see the black shiny flakes of Anthraxolite that surround or leak from these pockets. Anthraxolite is a carbon compound and by-product formed when organic material breaks down.

So as the organic material decayed and broke down it became a gas, trapped below layers of sedimentary stone. Air creates its own pressure inside a substance, so the air pressure was carving out its own cavity from the inside out. These air pockets became the pockets we rockhounds discover as we crumble, break, and peel away layers of the dolostone. Over the course of 200-250 million years the layers of sedimentary rock increased and grew, and this increased the pressure and heat on the buried dolostone. Also inside each of these air pockets were various quartz and carbon elements and other compounds "feeling the heat" from being buried below layers of sedimentary rock.

Under this pressure of the sedimentary layers of rock, and the ensuing heat, the quartz and other compounds inside these pockets began to transform themselves. Finally, over the course of 300 million years, the glaciers that sat atop Herkimer County began to melt, and washed away layers of the sedimentary rock, and allowed the compounds and elements inside these pockets to cool down and then crystallize.

An important question to answer right now is "why are the Herkimer Diamonds double-terminated?" The answer is that quartz does not adhere to the dolostone, therefore the quartz trapped inside these air pockets did not attach to the surrounding matrix host stone. The process left the quartz crystals free to fully crystallize unattached and allowed both of the ends to grow into fully terminated points. Many Herkimer Diamonds are found as clusters attached to one another. They adhered to one another during their crystal growth formation, but again did not adhere to the dolostone interior of the air pocket. The value of Herkimer Diamonds is determined by size and their opacity or translucence. The larger and more translucent Herkimer Diamonds are worth more to a collector or jeweler than the smaller opaque specimens. Knowing the history and background of the Herkimer Diamond however lends a premium in our opinion when you are considering adding Herkimer Diamonds to your collection. They are not commercially mined due to various New York state laws limiting mining in the state, and most of Herkimer County is being used today by happy grazing cows, sugary apple orchards, tart cherry trees, farms of squash, cabbages and onions, and wine grapes. We have recently gained access to heretofore unmined and barren acres in the Herkimer County area on the same geologic slope and ledge as the traditional Herkimer Diamond mines. We are in consultation right now with the owner about constructing a pole-barn over this new Herkimer mine so we can mine year-round. Follow our rockhounding adventures on Twitter, and here to keep updated on this exciting new venture to discover the first new Herkimer Diamond mine of the 21st century.

If you have questions about a gem, stone, fossil, or artifact that you have stumbled upon contact us via email or Twitter and we will try to help identify it with you. Rockhounding combines a sense of adventure with the science of exploration. We are continuously building a social rockhound community joining people far and near. Follow us on Twitter for our latest adventures and experience the joy of rockhounding. We strive to be kind and friendly in business and life. Do you have what it takes to be a rockhound?

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