Herkimer Diamond: What is It, Where to Find It

Herkimer Diamonds are double-terminated quartz crystals that are found in and around Herkimer County, New York, USA.

What is Herkimer Diamond

Herkimer diamond is a type of double-terminated quartz crystal found primarily in Herkimer County, New York, from which it gets its name. Although they are called "diamonds," Herkimer diamonds are not actually diamonds; they are a unique and particularly clear form of quartz that often has remarkable clarity and natural faceting.

Herkimer Diamonds are thought to have formed over 500 million years ago, when the Mohawk Valley region was covered by a shallow sea. The quartz crystals formed in cavities in the seafloor, and were eventually buried by sediment. Over time, the sediment hardened into rock, and the quartz crystals were preserved.

Double-terminated quartz crystals, commonly known as Herkimer diamonds.

Key Characteristics of Herkimer Diamonds

Double Termination: Unlike typical quartz crystals, which grow with a single point, Herkimer diamonds naturally form with points on both ends, giving them a "double-terminated" structure. This happens because they grow in pockets of dolostone (a type of sedimentary rock) where they are free to develop points on both sides without attachment to a host rock.

Exceptional Clarity and Sparkle: Herkimer diamonds are known for their clarity, often being exceptionally clear and transparent, with a glassy, diamond-like sparkle. They are sometimes almost water-clear but can also contain small inclusions, air bubbles, or black carbon deposits, which add character to each stone.

Natural Faceting: Herkimer diamonds often form with 18 natural facets and are already well-shaped when they are mined, which reduces the need for cutting and polishing compared to other crystals.

Composition: Despite their name, Herkimer diamonds are not carbon-based diamonds. They are made of silicon dioxide (SiO₂), the same as regular quartz. Their “diamond” name comes from their clarity, brilliance, and naturally occurring crystal form, which resembles cut gemstones.

Size and Rarity: Herkimer diamonds are typically small, with most crystals being under an inch long. Larger, high-clarity Herkimers are rare and highly valued by collectors and jewelry makers.

Colors: Herkimer diamonds can be found in a variety of colors, including clear, white, brown, and black.

Herkimer Diamonds

Inclusion: A fluid inclusion is a pocket within a crystal containing liquid, usually water, sometimes also methane or oil, and rarely, smaller crystals. A phantom is a crystal containing other visible crystals of the same type, a skeletal crystal contains a series of crystal edge outlines inside the crystal and a hopper crystal has its faces replaced by a step like pattern.

Herkimer Diamond. Photo: Northern Maine Minerals

Where to find Herkimer Diamonds

Herkimer diamonds are a popular tourist attraction in upstate New York. There are several commercial mines where visitors can dig for their own diamonds. Herkimer diamonds are also available from many rock and gem shops around the world.

Herkimer Diamond Mine, Herkimer county, New York

The undisputed king of New York gem digging, this iconic location is famous for its "diamonds" (double-terminated quartz crystals). They offer public and private digging areas, with beginner-friendly instruction, guided tours, and even educational exhibits.

Their website provides detailed information, pricing, and even a virtual tour: Herkimer Diamond Mines

Address: 4626 State Route 28 North Herkimer, NY 13350

Grove Diamond Mine, St. Johnsville, New York

Crystal Grove Diamond Mine is the place to go to find Herkimer diamonds, beautiful quartz crystals that are fun to mine. These crystals were first discovered in New York, and the perfect clarity of some of these stones makes them very popular with gem hunters.

Crystal Grove boasts a relaxed atmosphere and family-friendly amenities. They offer public and private digging areas, along with on-site camping facilities.

Fees: Adults (13 and up) pay $15 to mine, kids (6-12) pay $10, and kids under 5 are free. Camping fees are $30 per night for tent sites, $40 per night for RV sites with water and electric, and $50 per night for RV sites with full hookups. The mine is open from 9am to 5pm, seven days a week.

The Old Forge Gem Mine in Old Forge, New York

Old Forge Gem Mine is a gemstone mining operation located in Old Forge, New York. It is a family-owned and operated business that has been in operation since 1963. The mine offers a variety of gemstones to mine, including garnets, amethysts, tourmalines, and smoky quartz. The mine is open year-round, but the best time to visit is during the summer months when the weather is warm and sunny. There is a small fee to enter the mine, and all equipment is provided. Visitors are allowed to keep any gemstones that they find.

Additional information about the Old Forge Gem Mine:

• It is located at 2888 State Route 28, Old Forge, NY 13420.
• The phone number is (315) 369-4451.
• The hours of operation are 9am to 5pm, seven days a week.
• The admission fee is $10 for adults, $8 for seniors, and $5 for children ages 6-12. Children under 5 are free.

What is Herkimer Diamond, Where to Find Herkimer Diamond? © Rainbow Doorways.

Tips for finding Herkimer Diamonds

• Go during the spring or fall, when the weather is cooler and less humid.
• Look for rocks with small, dark holes. These holes are called "vugs," and they are most likely to contain Herkimer diamonds.
• Use a hammer and chisel to break open the rocks.
• Be patient! It can take some time to find Herkimer diamonds.

Aesthetic Herkimer Diamond Matrix specimen found at the “Ace of Diamonds Mine” in Middleville NY. Photo: Frank J McGivern Jr

In summary, Herkimer diamonds are not true diamonds but rather a special variety of quartz with a diamond-like appearance, prized for their clarity, natural shape, and distinct double-terminated points.