New Mexico Mineral Symposium — Abstracts

Hubnerite occurred sparingly throughout the San Juan Mountains in polymetallic veins as micro to cabinet size free-growing crystals in vugs and bladed crystal groups embedded in quartz. The monoclinic crystals are typically flattened and elongated, commonly showing fine striations parallel to the C axis. The crystals show a wide range of color from ruby to dark red to brownish red to black.

The chemical formula for hubnerite is Mn²⁺WO₄ and forms a solid solution series with ferberite (Fe²⁺WO₄). Wolframite, (Fe, Mn)WO₄ is a discredited mineral name that was used for material that was classified as an iron-manganese tungstate. Specimens that contain more than 80% manganese are hubnerite and conversely specimens that contain more than 80% iron are ferberite. Ferberite has not been reported from the San Juans, but iron-rich hubnerite, labeled wolframite, occurred at scattered localities in San Juan County, especially the Little Dora mine.

The type locality for hubnerite was the Erie and Enterprise mines, Nye County, Nevada, where it occurred as coarse red-brown blades associated with scheelite and fluorite. The mineral was named after Professor Adolph Hubner, a German mining engineer at the Freiburg School of Mines, Saxony, Germany. In 1885, hubnerite was first found in Colorado at the Royal Albert mine, Ouray County, where it occurred as long-bladed, vertically striated crystals embedded in quartz.

Hubnerite occurred in Ouray County at a number of localities where it usually formed micro crystals associated with other minerals. At the Camp Bird mine it occurred as micro crystal inclusions in scheelite. The best locality in Ouray County was at the Grizzly Bear mine, where it formed beautiful free-growing micro crystals associated with quartz, rhodochrosite, pyrite, and sphalerite.

In San Miguel County, the best occurrence was in the Idarado mine where it formed ruby to dark red crystals up to 6 mm in length scattered on crystallized quartz.

The most outstanding localities for hubnerite are all located in San Juan County. The famous Sunnyside mine, known for outstanding rhodochrosite and fluorite crystal groups also produced beautiful specimens of free-growing hubnerite crystals up to 3 cm long. Most of the specimen-producing mines are in a belt along Cement Creek and locally have been called the "Cement Creek tungsten district." Commercial quantities of hubnerite in many of the veins along the belt were mined sporadically from 1900 to the 1980s. Much of the ore was hand-sorted, and the mines only operated during periods when the price of tungsten was high. Hundreds of high-quality specimens were produced over the years from this group of mines.

The premier locality for hubnerite in the San Juans is the Adams mine (aka Adams lode), located on Bonita Peak, San Juan County. At this locality, the hubnerite formed groups of long-bladed crystals up to 8 cm long. The reddish-brown crystals usually are embedded in a massive crystalline quartz and are etched with a hydrofluoric solution to remove the quartz. The resulting specimens are world-class and grace many major mineral collections.

Mining has ceased in the San Juans, but good micro crystals of hubnerite can be found on many of the mine dumps in Ouray and San Juan Counties.