8.21 ct HUEBNERITE – USA

Hübnerite
Hübnerite is a mineral that commands respect the moment you see its deep, blood-red transparency held against the light. It is the manganese-rich endmember of the Wolframite series, and while its industrial cousin, Ferberite, is often just a dense black mass, a high-quality Hübnerite crystal offers a level of optical depth that is rare in the world of metallic oxides. I have always been drawn to its weight and its adamantine luster—it has a “heavy” brilliance that feels different from a silicate gemstone. It isn’t just a specimen of tungsten ore; when you find a crystal clear enough to facet, it becomes a brooding, crimson gem that holds its own against any of the more traditional rare stones in the vault.

The Heritage & Discovery

Historical Significance: Hübnerite is a vital part of the Wolframite group, which has historically been the world’s primary source of tungsten. Beyond its industrial importance in hardening steel, it has become a holy grail for collectors of metallic minerals. Its presence in a collection represents the intersection of heavy-metal chemistry and the high-temperature hydrothermal environments where it thrives, often alongside quartz and fluorite.

Discovery: The mineral was first described in 1865 by Friedrich Adolph Roemer. It was named in honor of the German mining engineer and metallurgist, Adolf Hübner. Since its identification, it has been the subject of intense study due to its perfect solid-solution series with iron, where the ratio of manganese to iron dictates whether the stone is a true Hübnerite or its darker sibling, Ferberite.

Important Mines: The most iconic, transparent red crystals—the ones I search for to attempt faceting—usually come from the high-altitude mines of Pastos Bueno, Peru. Other world-class specimens have emerged from China and the Panasqueira Mine in Portugal. The Peruvian material, however, remains the gold standard for those seeking that rare “ruby-red” translucency in a heavy metallic matrix.

Mineralogical Profile

Description: Hübnerite is a manganese tungsten oxide that crystallizes in the monoclinic system. It sits at a 4 to 4.5 on the Mohs scale, making it relatively soft but durable enough to take a high, sub-metallic to adamantine polish. Its most striking feature is its sub-transparency; while the crystals look black at first glance, thin sections or faceted edges reveal a deep, fiery red or yellowish-brown color. It is a dense mineral with a high refractive index, giving it a sharp, mirror-like surface when correctly worked.

Chemical Formula: MnWO₄