Hamberg Mine, Arizona — The Forgotten Source of Deep Red Vanadinite

Yunkuan Wu
Oct 13
4 min read

When collectors think of Arizona mineral localities, the Red Cloud Mine often takes the spotlight, renowned worldwide for its brilliant red wulfenite crystals. Yet, just a mile to the northeast lies another deposit that once rivaled it in fame among vanadinite enthusiasts: the Hamberg Mine, often spelled Hamburg. Though far less celebrated today, it stands as one of the most historically significant vanadinite localities in the American Southwest, producing crystals that rival and often surpass those from other Arizona sites in brilliance and depth of color.

Vanadinite xtls - Hamburg Mine, Silver Mining District, La Paz County, Arizona, USA

A Glimpse into History

The Hamberg Mine sits in the Trigo Mountains in Yuma County, Arizona, a rugged desert region marked by steep canyons, dark andesite ridges, and a silence broken only by the desert wind. It was first located in the 1860s as part of the Silver District’s early silver lode claims. During 1880 and 1881, geologist William P. Blake and others sank an inclined 18 meter shaft into the hillside, followed by a short horizontal drift. Although no commercial ore was ever extracted, the true treasure was not silver but the brilliant vanadinite crystals that collectors began to discover in the late nineteenth century.

Old mineralogists such as Benjamin Silliman Jr. in 1881 praised Hamberg’s specimens as “the most numerous and, on the whole, the best” vanadinites of the district. Over time, however, confusion arose between the Hamberg, Princess, and Red Cloud mines, which are all situated along the same mineralized fault zone. Many specimens labeled Red Cloud were in fact collected at Hamberg.

Vanadinite xtls on white calcite matrix - Hamburg Mine, Silver Mining District, La Paz County, Arizona, USA

Geology and Formation

Vanadinite occurs in brecciated silicified andesite that is cut by quartz seams within Precambrian schist and granite, later affected by younger volcanic activity. These veins were emplaced along a fault system that also hosts the nearby Red Cloud deposit. The vanadinite bearing zone appears at about the twelve meter level of the mine and is bordered by iron stained andesite, a clear sign of oxidation of lead rich minerals such as galena.

Within these fractures, nature created countless cavities lined with gemlike hexagonal prisms of vanadinite, whose chemical formula is Pb₅(VO₄)₃Cl. Over long periods of time, the slow oxidation of vanadium rich lead minerals in arid desert conditions produced the vivid red crystals that made Hamberg famous.

The Crystals — Desert Jewels of Fire

Hamberg Mine vanadinite is immediately recognizable. Crystals range from microscopic size to more than 1.5 centimeters, often forming on gray quartz or calcite matrix. Their color is a deep red, often compared to the glow of a car taillight, with exceptional transparency and luster. Many crystals show hopper growth, where the edges grow faster than the centers, creating delicate skeletal forms with stepped faces. Under magnification, these hollow hexagonal prisms gleam like tiny crimson lanterns.

Although most crystals are pure red, some display subtle orange red or yellow zoning, a sign of small variations in oxidation and trace elements during growth.

Associated Minerals

While vanadinite is the star, the Hamberg Mine also produces several other secondary lead minerals:

Wulfenite (PbMoO₄): Orange red tabular crystals up to 1.5 centimeters, similar in appearance to those from Red Cloud.
Mimetite (Pb₅(AsO₄)₃Cl): Minute yellow tufts found near wulfenite veins.
Anglesite (PbSO₄) and Cerussite (PbCO₃): Often replacing galena in small pods.
Traces of lead oxides such as minium, litharge, and massicot that tint the rock with red and yellow tones.

Collecting and Conditions

Reaching the site is an adventure in itself. The Trigo Mountains are part of the low desert, where temperatures above fifty degrees Celsius are common in summer. There is no water, no shade, and no mercy from the heat. The rough trail beyond the Red Cloud Mine often turns what appears to be a short drive into a two hour test even for experienced off road drivers. Collectors usually visit in winter, when the air cools to a pleasant twenty to twenty five degrees and the scent of creosote bushes drifts through the canyons.

Legacy and Confusion

For many decades, vanadinites from the Hamberg, Princess, and Romaldo Pachecos mines were mislabeled as Red Cloud specimens. Even the Smithsonian Institution holds nineteenth century pieces labeled “Romaldo Pachecos Mine” that were probably collected at Hamberg. Modern mineralogists, including Wendell E. Wilson of The Mineralogical Record, have helped to clarify the history and restore the Hamberg Mine’s rightful status as the true source of some of the finest deep red vanadinite ever found in Arizona.

A Desert Flame That Endures

Today, specimens from the Hamberg Mine are prized by collectors for their intense color, clarity, and historical importance. Each crystal is a spark of the desert’s geological story, formed through the meeting of lead, vanadium, and time. Though the mine itself has long fallen silent, its vanadinite continues to shine in collections and museums around the world, reminding us that even forgotten places can hold extraordinary treasures.