78.00 ct MOHAWKITE – USA

Mohawkite

Mohawkite represents the “shadow-metallic” rarity of the copper-rich world. A rare mixture of copper, arsenic, and cobalt—specifically a variety of Domeykite—it is a species I have always respected for its incredible density and its “hidden” colorful potential. When fresh, it presents as a stark, metallic grey to silver, but it is best known for its ability to take a spectacular, mirror-like polish that reveals a “golden-bronze” glow. For the specialist, Mohawkite is a prize of elemental concentration; it is found only in a single geological environment on Earth, making it one of the most geographically restricted materials in the collection. It is a stone of “industrial mystery,” providing a sophisticated, “liquid-metal” aesthetic that makes it a true “frontier” specimen for the systematic vault.

The Heritage & Discovery

Historical Significance: Mohawkite is a vital species for understanding the unique “Native Copper” mineralogy of the American North. Historically, it was discovered during the height of the copper mining boom in the 19th century, but because it contained arsenic, it was often discarded by miners as “poisoned ore.” In the world of fine minerals, it has been reclaimed as a lapidary treasure, celebrated for the way it mimics the appearance of gold or platinum when expertly finished. It stands as a symbol of local heritage and overlooked beauty, bridging the gap between heavy metal mining and the elite world of “one-locality” collector gems. It serves as a reminder that the most “discarded” minerals of the past can become the most sought-after rarities of the present.

Discovery: The mineral was formally named in reference to its type-locality: the Mohawk Mine in the Keweenaw Peninsula. Scientifically, it is an arsenide of copper. Its discovery provided mineralogists with the first clear look at how copper and arsenic can co-crystallize into a stable, high-density metallic mass without the presence of sulfur. My own respect for this material is rooted in its rare “sheen”; because it often contains trace amounts of nickel and cobalt, the polished surface has a “depth” of color that common copper alloys cannot achieve. Since its identification, it has become a “must-have” for collectors of “Native” element mineralogy.

Important Mines: The undisputed and only world capital for this material is the Mohawk Mine (and the nearby Ahmeek Mine) in Keweenaw County, Michigan, USA. No other location on the planet produces this specific “Mohawkite” mixture. For the vault, I prioritize pieces that show the characteristic “golden-bronze” tarnish and the high-density weight that is the definitive signature of the Michigan copper country.

Mineralogical Profile

Description: Mohawkite is a copper arsenide mixture that crystallizes in the isometric system (as part of the Domeykite-Algodonite series). It sits at a 3 to 3.5 on the Mohs scale, making it a relatively soft metallic material that requires a high-end polish to maintain its luster. It is characterized by its metallic luster and its shift from silver-grey to a warm, “brass-like” bronze upon exposure.

One of its most identifying traits is its extreme specific gravity ($SG \approx 7.2$ to 8.0), which gives it a “heavy” feel that rivals Lead or Silver. It has an opaque diaphaneity and a characteristic metallic streak. Because it forms in the hydrothermal veins of the Keweenaw, it is often found in association with Native Copper, Silver, and Quartz. When I select a piece for the collection, I look for “solid” masses with no internal “vugs” or pits, as these allow for the most sophisticated, three-dimensional polish. It is a dense, high-vibration mineral that offers a unique, “industrial-chic” beauty unlike any other metallic species.

Chemical Formula: Cu₃As (+ Ni, Co)