As an antique collector and gemstone expert with over 20 years of experience, I‘ve had the pleasure of handling many exceptional Herkimer diamonds. These rare and beautiful quartz crystals, named for the Herkimer County region of New York where they were first discovered, have captivated collectors for centuries with their brilliant clarity, natural facets, and diamond-like luster. But for those new to Herkimer diamonds, understanding what influences their value can be confusing. In this in-depth guide, I‘ll share my knowledge and insider tips for evaluating and pricing Herkimer diamonds.
The History and Lore of Herkimer Diamonds
Herkimer diamonds have a long and fascinating history. According to geologists, these double-terminated quartz crystals formed over 500 million years ago in the dolomitic limestone beds of what is now central New York state. But they remained hidden underground until the late 18th century, when settlers reportedly discovered them while excavating the area‘s rocky soil.
The unique crystals quickly caught the attention of lapidaries and jewelry makers, who prized them for their clarity and brilliance. By the mid-19th century, Herkimer diamonds were being mined commercially and set into everything from simple pendant necklaces to elaborate brooches and hair combs in the Victorian style.
Esoteric and metaphysical traditions have long ascribed special properties to Herkimer diamonds. In crystal healing, they are believed to have powerful energetic vibrations that can amplify spiritual awareness, increase psychic sensitivity, and promote inner vision. Some even claim that Herkimer diamonds can enhance dream recall and facilitate astral travel. While these metaphysical associations don‘t directly impact value in the same way as physical qualities like size and clarity, they do contribute to Herkimer diamonds‘ enduring popularity among certain collectors.
Evaluating Herkimer Diamonds: The Four Cs
As with other gemstones, Herkimer diamonds are graded based on the "Four Cs" – color, clarity, cut, and carat weight. Here‘s a detailed look at how each factor influences Herkimer diamond value:
Color
The ideal Herkimer diamond is completely colorless, like a high-quality white diamond. But many Herkimer diamonds have slight hues, typically pale yellow, golden, smoky gray, or brownish. Generally, the closer to colorless, the higher the value. In some rare cases, Herkimer diamonds may exhibit a natural pale pinkish or reddish tint, which can actually increase their value if the color is even and not the result of heat treatment.
Color grades for Herkimer diamonds are as follows:
| Grade | Description |
|---|---|
| AA | Colorless, transparent |
| A+ | Near colorless, slight tint barely visible |
| A | Noticeably tinted (pale yellow, brown, gray) |
Clarity
Clarity refers to the presence or absence of internal and external flaws, or inclusions. Because Herkimer diamonds are a type of macro-crystalline quartz, most have at least some minor inclusions. But the clearest, most valuable Herkimer diamonds have no eye-visible inclusions when viewed from the top. Flaws that can lower value include:
- Clouds, shadows, or ghostly wisps
- Interior cracks or fissures
- Foreign mineral crystals
- Hollow tubes or large bubbles
- Obvious surface flaws or chips
Herkimer diamonds are clarity graded as follows:
| Grade | Description |
|---|---|
| VVS | Very very slightly included, no eye-visible inclusions |
| VS | Very slightly included, minor inclusions visible close up |
| SI1, SI2 | Slightly included, noticeable inclusions under 10x magnification |
| I1, I2, I3 | Included, obvious inclusions visible to the naked eye |
Some Herkimer diamonds contain black carbon crystal inclusions that resemble flecks of pepper. While these can create attractive patterns, they do detract somewhat from overall value compared to cleaner stones.
Clarity has a significant impact on value. Flawless VVS Herkimer diamonds may sell for 2-3x more per carat than heavily included I1-I3 stones. To illustrate:
| Size | VVS Price per Carat* | I1-I3 Price per Carat* |
|---|---|---|
| <1 ct | $200-300 | $50-100 |
| 1-2 ct | $300-500 | $100-200 |
| >2 ct | $500-1,000+ | $200-400 |
*Prices are estimates for well-cut stones with good color. Actual prices may vary.
Cut
The cut of a Herkimer diamond refers to its proportions, symmetry, and overall finish. But unlike most other gemstones, Herkimer diamonds are not traditionally cut by human hands – their shape and facets occur naturally as a result of their unique crystalline structure.
The most classic and desirable Herkimer diamond shape is the "double terminated" crystal – a hexagonal prism capped by two offset pyramids, one on each end. This distinctive form is instantly recognizable and an essential part of Herkimer diamonds‘ identity. The more symmetrical and clearly defined the terminations, the better.
Herkimer diamonds may have up to 18 natural facets (7 or 8 on each termination plus 2-4 around the middle). The most valuable Herkimer diamonds have sharp, undamaged facet edges and an appealing overall geometry. Avoid stones with chipped, worn, or asymmetrical facets.
While Herkimer diamonds can be cut or polished into other shapes like rounds, ovals, or trilliants, these modified stones are typically much less valuable than natural crystals of equivalent quality. The exception is if the Herkimer diamond has been cut to remove significant flaws while preserving its double termination.
Carat Weight
Herkimer diamonds range in size from tiny drusy crystals under 1mm to massive museum specimens weighing several pounds. From a collector‘s perspective, the "sweet spot" in terms of value is generally between 10-50 carats. These stones are large enough to show Herkimer diamonds‘ characteristic shape and brilliance, but not so big as to be impractical for jewelry.
All else being equal, larger Herkimer diamonds are rarer and command higher prices per carat than smaller stones. To give a rough idea, here are some sample prices for Herkimer diamonds of different sizes:
| Size | Price per Carat* |
|---|---|
| <1 ct | $50-200 |
| 1-5 ct | $100-500 |
| 5-10 ct | $200-800 |
| 10-25 ct | $500-1,500 |
| 25-50 ct | $1,000-3,000 |
| >50 ct | $2,000-10,000+ |
*For natural, untreated stones with very good color and clarity. Prices may vary.
Of course, these are just guidelines – exceptional Herkimer diamonds of any size can sell for much more. In 2012, a flawless 18.92 carat Herkimer diamond set an auction record when it sold for $18,750 ($991 per carat) at Heritage Auctions in Dallas. More recently in 2020, a stunning 75.43 carat Herkimer diamond fetched $18,000 ($239 per carat) at Bonhams Los Angeles.
While larger Herkimer diamonds are usually more valuable, bigger is not always better from a collector‘s standpoint. The most important factors are still color, clarity, and cut – a small but flawless Herkimer diamond will always be worth more than a huge stone riddled with unsightly inclusions.
Other Factors Influencing Herkimer Diamond Value
Beyond the Four Cs, there are a few other things that can impact what a Herkimer diamond is worth:
Treatments
As with other gems, any treatments or enhancements made to a Herkimer diamond after it comes out of the ground will lower its value compared to a natural, untreated stone. The most common treatments are:
- Heat treatment to improve color or clarity
- Irradiation to induce color
- Fracture filling to conceal cracks
- Coating to create an iridescent sheen
Reputable Herkimer diamond sellers should always disclose any known treatments up front. To be safe, assume that any stone with unusually vivid color or flawless clarity for its price has likely been treated in some way.
Famous Provenance
As collectors, we know that a great backstory can add both allure and value to an item. The same goes for Herkimer diamonds with a notable history or provenance. Specimens that were mined during the earliest days of Herkimer diamond discovery in the 19th century and owned by prominent collectors of the past can fetch a premium.
One example is the "Canfield Diamond", a 12.7 carat Herkimer named after its original owner Frederick Canfield, a pioneering mineralogist who helped put Herkimer diamonds on the map in the late 1800s. This historically significant stone is now in the collection of the New York State Museum in Albany.
Herkimer diamonds set in antique or vintage jewelry by famous makers like Tiffany & Co. or Cartier also tend to be highly prized by collectors. An Art Deco platinum and Herkimer diamond ring, circa 1925, could easily sell for 2-3 times what the Herkimer diamond alone is worth.
Origin and Mining Conditions
All authentic Herkimer diamonds come from Herkimer County or the adjacent Mohawk River Valley in upstate New York. But not all Herkimer diamond mines are created equal in terms of quality and value.
Certain historic mines known for producing top grade crystals, such as the Ace of Diamonds Mine, Diegel Mine, and Crystal Grove Diamond Mine can add to a Herkimer diamond‘s cachet and collectibility. Herkimer diamonds from other countries or unnamed sources should be evaluated with caution – they may not be true Herkimer diamonds at all.
The way in which a Herkimer diamond was mined can also have an impact, especially to collectors who prioritize untouched natural specimens. Herkimer diamonds that were carefully hand-collected from the rock matrix are generally more highly valued than those extracted using heavy machinery or blasting, which can cause chips and fractures.
How to Identify Real Herkimer Diamonds
Unfortunately, as with many sought-after gemstones, there is no shortage of fakes and lookalikes on the Herkimer diamond market. Common imposters include glass, synthetic quartz, zircon, topaz, and even colorless sapphire – all masquerading as the real thing.
As a collector, knowing how to spot a true Herkimer diamond is essential for getting your money‘s worth and avoiding costly mistakes. Here are some key things I always check:
Shape and Structure
First, look at the overall shape and geometry of the stone. Remember, a genuine Herkimer diamond should have:
- Double termination (two pointed ends)
- 18 total facets (6 on each end plus 6 around the middle)
- A hexagonal cross-section
If the stone has only one termination, is too symmetrical, or lacks natural-looking facets, it‘s likely not a Herkimer diamond. But some dealers do cut or polish the ends, so this alone doesn‘t necessarily mean it‘s fake.
Hardness
Herkimer diamonds are quartz, which means they have a Mohs hardness of 7 to 7.5. You can test this by seeing if the stone can scratch glass. If it can‘t, it‘s definitely not a Herkimer diamond. But be careful – plenty of imitations like synthetic moissanite are also hard enough to scratch glass.
Inclusions
Check the stone closely for common Herkimer diamond inclusions like black carbon specks, wispy veils, or bubbles. If the stone is too perfect inside, especially given the price, be suspicious. On the flip side, obvious cracks, chips, or foreign material stuck to the surface are red flags too.
Specific Gravity
Herkimer diamonds have a specific gravity of 2.65, meaning they will sink in a liquid with SG greater than 2.65. You can buy heavy liquids for this test from a jewelry supply store. If your stone floats, it‘s not a Herkimer diamond – but this test can‘t rule out all possible imposters.
The bottom line? If you‘re spending serious money, it‘s always best to have the stone evaluated by a qualified gemologist or appraiser specializing in Herkimer diamonds. Established dealers should provide a certificate of authenticity for high-value stones. Trust your gut – if a Herkimer diamond deal seems too good to be true, it probably is.
Caring For and Storing Herkimer Diamonds
With a hardness second only to diamonds and sapphires, Herkimer diamonds are thankfully quite durable and easy to care for. To keep them looking their sparkling best, simply clean your Herkimer diamonds regularly with warm water, mild dish soap, and a soft toothbrush. Never use harsh chemicals, ultrasonic cleaners, or steam cleaners, which can damage the surface or cause cracking.
I always recommend storing Herkimer diamonds separately from other jewelry to prevent scratches. Wrap each stone in a soft cloth and place in a padded jewelry box, or tuck into individual silk or velvet pouches for safekeeping. If you‘re displaying Herkimer diamonds long-term, be sure to keep them out of direct sunlight which can cause fading over time.
Final Thoughts
Herkimer diamonds have been prized for their unique beauty and inner fire for centuries, and their allure shows no signs of dimming. Whether you appreciate Herkimer diamonds as glittering artifacts of the earth‘s geologic history, powerful metaphysical talismans, or simply stunning jewels in their own right, these multifaceted marvels are sure to hold their value and fascination for generations to come.
By understanding the key factors that impact Herkimer diamond prices and being aware of potential pitfalls in the market, you‘ll be well equipped to build or expand a collection that will bring you joy for years to come. And who knows – you may just be lucky enough to unearth the next record-breaking Herkimer diamond!
I hope this guide has given you a solid foundation for evaluating and appreciating the amazing world of Herkimer diamonds. Happy hunting!
