By Christina Sloane, updated March 24, 2022
Herkimer diamonds are not true diamonds; they are a distinctive form of quartz found only in a handful of locations worldwide, most famously in Herkimer County, New York. Their naturally faceted, double‑terminated crystals can sparkle brilliantly when properly cleaned. This guide walks you through a safe, at‑home cleaning routine and explains what makes these quartz gems unique.
To reveal the true brilliance of your Herkimer diamonds, regular cleaning is recommended—especially if you collected them from the field.
Lightly Soaked Cleaning
For most specimens, simply soak them in warm water for 5–10 minutes. Swirl the bowl gently to agitate the water, then lift the crystals out and let them air‑dry on a towel. This removes loose dust and brings out subtle inclusions.
Deeper Cleansing for Stubborn Debris
If your crystals still look dull, add a couple of drops of dish soap to the warm water. After soaking for about 15 minutes, use the soft brush to gently scrub the faces and the narrow crevices. Rinse thoroughly with clean water and allow the stones to dry in a warm, well‑ventilated area.
These quartz crystals are naturally faceted, with 18 planes and two sharp terminations—hence the term “double‑terminated.” They rank 7.5 on the Mohs hardness scale, compared to 10 for true diamonds. While most are clear and colorless, some display smoky tones due to tiny inclusions such as anthracite (decayed plant matter) or microscopic air pockets, giving them a unique visual appeal.
For collectors, Herkimer County remains the premier location. Numerous commercial mines along Routes 28 and 29 near Middleville offer tours and rental tools—crack hammers, chisels, wedges, and pry bars—for exploring the quartz‑rich bedrock. If you venture into these sites, safety is paramount: wear goggles, long pants, a long‑sleeved shirt, closed‑toe shoes, and gloves. Prospecting can be a fun family activity, and any crystals you retrieve are yours to keep after a quick cleaning.
