Berg Aukas descloizite is one of the great “species-defining” classics: the locality by which serious collectors judge descloizite. The best pieces have a sculptural, almost architectural presence—dark brown to nearly black spear-point crystals, glossy blades, jackstraw bundles, radiating rosettes, and sharply terminated clusters that can look metallic under a show lamp yet glow warm reddish brown along thinner edges. Many specimens sit in pleasing contrast on pale calcite, dolomite, smithsonite, or willemite-bearing matrix, giving the dark vanadate crystals the visual authority of black lacquer against limestone.
Photo: Wikimedia Commons
The mineralogical setting explains both the abundance and the form. Berg Aukas is a Zn-Pb-V deposit in the Otavi Mountainland, hosted by carbonate rocks of the Otavi Group. The mine’s famous descloizite formed in the oxidized, supergene part of the deposit, especially in vugs, fractures, karst cavities, and collapse breccias adjacent to zinc ore rich in smithsonite and willemite. In a typical lead-zinc deposit, descloizite is a minor secondary mineral, often microscopic. At Berg Aukas it became an ore mineral and a display mineral at the same time.
Photo: Wikimedia Commons
Collectors prize Berg Aukas pieces for sharpness, heft, and drama. The finest miniatures and small cabinet specimens show isolated, complete spearheads; others are dense masses of intergrown blades or rosettes, sometimes crystallized on multiple sides. The classic colors range from orange-brown and golden brown through deep chocolate and greenish black to lustrous black. The best crystals have clean terminations, no bruised tips, a bright greasy-to-subvitreous luster, and enough translucency or internal red-brown glow at the edges to distinguish them from merely dark masses.
Historically, Berg Aukas matters because it was not just a specimen locality; it was a vanadium mine of global mineralogical importance. The deposit was discovered in 1913, worked intermittently in the 1920s, reopened for fuller production in the mid-20th century, and closed in 1978. That closure fixed the supply of classic Berg Aukas descloizite. Today nearly every good specimen on the market is old stock, an ex-collection piece, or a recycled show specimen from material recovered during the mine’s productive decades.
Search for specimens: View all descloizite specimens from Berg Aukas Mine, Namibia
Berg Aukas Mine lies near Grootfontein in the Otjozondjupa Region of northern Namibia, within the Otavi Mountainland. The locality is also encountered on older labels as “Berg Aukus,” “Grootfontein District,” or, on pre-1990 labels, South West Africa. The deposit is a lead-zinc-vanadium system hosted by dolostone, limestone, and shale of the Berg Aukas Formation at the base of the Abenab Subgroup of the Otavi Group. Structurally, the mine sits on the northern limb of the Berg Aukas Syncline.
The ore geology is more complex than a single “pocket” locality. Published mine descriptions distinguish the Northern Ore Horizon from the Central, Intermediate, and Hanging Wall ore bodies. The Northern Ore Horizon consisted of oxidized lenses along a contact between grey dolomites, with sphalerite, galena, and subordinate pyrite as primary sulphides and descloizite, willemite, cerussite, smithsonite, and goethite as common secondary minerals. The Central, Intermediate, and Hanging Wall ore bodies were more irregular, developed in recrystallized dolomite along steep north-south fractures, solution cavities, and karst-collapse structures. Those bodies contained disseminated galena and sphalerite in clay-, mud-, and sand-rich dolomitic material, with contacts locally lined by crystalline willemite.
The mine was discovered in 1913 when the apex of the Central Ore Body was found on top of a hill. Mining began in 1920 and stopped in 1928 after the workings reached groundwater. The mine was later reopened, and by the 1950s it had entered the production period that yielded many of the specimens now regarded as classics. Operations continued until closure in 1978. Reported ore grades include a mine average around 16.8 percent Zn, 4 percent Pb, and 0.93 percent V2O5, while reserves at closure have been reported at 1.65 million tonnes grading 17 percent Zn, 5 percent Pb, and 0.6 percent V2O5. Mineralization was traced to considerable depth, but the famous collector-quality descloizite belongs to the oxidized and supergene part of the system rather than the deep primary sulphide ore.
After closure, Berg Aukas did not become an easy collecting ground. The deeper workings flooded, old galleries were not securely sealed in places, and environmental studies have documented serious contamination of soils and mine remnants by lead, zinc, cadmium, arsenic, vanadium, and other metals derived from historic mining, roasting, smelting, tailings, and slag. The former mine area has also been reused for local settlement, training, and agricultural activity. For modern collectors, the practical conclusion is simple: Berg Aukas specimens should be considered a historical market resource, not a casual field-collecting opportunity.
Notable finds include the large and complete spear-point miniatures, thick all-around clusters, vug linings of lustrous tabular crystals, descloizite with calcite or dolomite, and rarer associations with smithsonite, willemite, mimetite, cerussite, vanadinite, and anglesite. The mine also produced important smithsonite and willemite specimens, but descloizite remains its signature mineral.
Berg Aukas descloizite is PbZn(VO4)(OH), the zinc-dominant member of the descloizite-mottramite series. The Berg Aukas material is famous because it occurs in hand-sized, collector-grade crystal groups rather than only as coatings or micromount material.
The most iconic habit is the spear-point blade: sharply terminated, flattened, elongated crystals that can resemble chiseled arrowheads. These may stand singly from a base of smaller crystals, form subparallel stacks, or intergrow into branching clusters. Other Berg Aukas habits include prismatic crystals, tabular blades, pyramidal crystals, pseudocubic forms, dense crystalline crusts, radiating rosettes, and vug linings. Mindat’s locality data describes crystals up to about 1 cm in vugs as aggregate bundles or radiating rosettes, while individual dealer and museum specimens show larger spear-point crystals on selected miniatures; documented specimens include crystals to about 2.3 cm on a 3.5 x 3.3 x 2.1 cm cluster.
Color is one of the great pleasures of this locality. Fresh-looking crystals may be golden brown, orange-brown, reddish brown, chocolate brown, greenish black, metallic black, or nearly black. Thin edges and broken or backlit areas can reveal a warm amber to red-brown translucency. Some pieces show an iridescent, bornite-like surface sheen, and some have tan carbonate overgrowths or coatings along blade edges. The luster is typically bright resinous, greasy, subvitreous, or highly reflective; collectors often describe the best black pieces as “metallic,” but the effect is usually an interaction of high refractive index, dark color, smooth faces, and strong reflected light rather than true metallic luster.
Associations are important for recognizing Berg Aukas material. Calcite and dolomite are the most common companion minerals in specimen descriptions and photo data. Smithsonite is also frequent, especially pale, beige, white, or greenish material, and willemite may occur as massive or crystalline zinc silicate. Mimetite, cerussite, anglesite, vanadinite, and minor goethite are also recorded from the locality. Matrix pieces with pale carbonate or smithsonite can be especially attractive because they give contrast to the dark descloizite blades; however, many classic Berg Aukas miniatures are essentially all-descloizite clusters with little or no visible matrix.
Quality is judged first by crystal form. A great Berg Aukas specimen has complete spear points, clean edges, and well-separated blades rather than a heavy, indistinct crust. Next comes luster: glossy faces and flashing terminations matter greatly. Color matters too, especially when the crystals show contrast between black faces and reddish-brown translucent edges. Aesthetic architecture is a major factor. Single dominant spearheads, radial sprays, open jackstraw groups, and balanced all-around miniatures bring stronger collector response than flat plates or massive ore chunks. Association can add value when the companion mineral improves contrast, but matrix is not required for a top-quality piece.
Typical specimen sizes range from thumbnails and miniatures to small cabinet pieces. Micromounts and small thumbnails are still obtainable and can be excellent under magnification. Fine miniatures are the sweet spot for many collectors: large enough to show the spear-point habit, small enough to be crisp and damage-free. Cabinet specimens exist and can be visually impressive, but large pieces often show contacted areas, bruised blade tips, or zones of massive descloizite rather than uniformly pristine crystals.
Berg Aukas descloizite is not rare in the absolute sense—many specimens entered collections during the 20th century—but fine specimens are finite, increasingly recycled, and much harder to replace than casual market appearances suggest. The mine closed in 1978, and serious pieces now surface chiefly through old collections, dealer back stock, estate dispersals, and auctions. Affordable thumbnails and small cabinet fragments still appear, but crisp, undamaged spear-point miniatures and aesthetic, all-around clusters are classic-level acquisitions.
Documented fake or treated Berg Aukas descloizite is not a major collecting problem compared with many colorful secondary minerals. The larger concern is attribution. Old labels may say only “Namibia,” “South West Africa,” “Grootfontein,” or “Berg Aukus,” and the Otavi Mountainland contains several vanadium localities whose descloizite and mottramite can be confused. Abenab, Abenab West, Uitsab, and other Otavi localities produced related material. Berg Aukas pieces tend to favor dark spear-point blades, subparallel groups, rosettes, and associations with calcite, dolomite, smithsonite, and willemite, but locality should still be evaluated by provenance, old labels, matrix, habit, and comparison with well-documented examples.
Another authenticity issue is species-level identification within the descloizite-mottramite series. Descloizite is zinc-dominant; mottramite is copper-dominant. Color alone is not a safe separator, and some Otavi vanadates are compositionally intermediate or copper-bearing. For expensive specimens, especially unusual greenish or very dark material without classic Berg Aukas habit, analysis or a strong chain of provenance is worthwhile.
Condition is the collector’s real battleground. Descloizite is brittle and only moderately hard, so spear tips, thin blade edges, and projecting crystals are vulnerable. Large clusters commonly have broken peripheral blades, bruised terminations, contacts from pocket walls, or old trimming damage. Bright luster can disguise small edge chips until the specimen is turned under low-angle light. Examine the terminations, not just the overall sparkle. On older pieces, also check for repaired bases, glued-on fragments, or stabilization of crumbly matrix, especially where descloizite sits on soft carbonate or clay-rich breccia.
Dust is common on vuggy and massive pieces, and aggressive cleaning is risky. Avoid acids unless a qualified preparator has tested the exact assemblage, because carbonate matrix and associated minerals can be damaged. Ultrasonic cleaning is generally unwise for bladed clusters. A soft brush, air bulb, and careful water cleaning on stable specimens are safer than attempts to make the luster artificially “pop.”
Market availability is broad at the low end and narrow at the high end. Small, dark, dense pieces can remain affordable. Miniatures with sharp spear points, excellent luster, translucency, and minimal damage command a premium. Specimens with strong old provenance—1970s labels, named collections, museum deaccession history, or classic dealer labels—are especially desirable because they reinforce both locality and historical authenticity.
Berg Aukas has one of the strangest origin stories in the mineral world because some of its descloizite can be read not only as ore, but as a fossil-bearing cave event.
In the Central Ore Body, blocks of fossil-rich breccia were found wrapped in crusts of large descloizite crystals, and those crystal crusts were themselves enclosed again in fossil-bearing breccia. One studied sample, Ber 42’92, showed descloizite grown directly on a chunk of pink fossiliferous breccia. The underside of the crystals molded the original shape and surface texture of that breccia, while the outer faces remained euhedral, meaning they had room to grow freely into open space. For a mineral collector, that is a remarkable image: dark vanadate crystals forming in a cave, gripping a fossil-rich fragment on one side and opening into a void on the other, then being buried again by later cave sediment.
That relationship gave geologists a rare clock. The breccias at Berg Aukas range from middle Miocene to Holocene, but the descloizite-rich breccia blocks studied by Martin Pickford were middle Miocene, about 13 ± 1 million years old. Later breccias—upper Miocene, Pliocene, Pleistocene, and Holocene—were either barren of descloizite or contained broken and reworked descloizite fragments. The result was a tighter age estimate than most old “supergene” labels ever provide: a major portion of the Berg Aukas descloizite deposit appears to have formed late in the middle Miocene, perhaps over only 1–2 million years.
The same breccias held a small ancient fauna. Pickford listed bats, insectivores, rodents, carnivores, and the primate Otavipithecus namibiensis from descloizite-rich Berg Aukas breccia. The bat remains are more than a footnote. The abundance of chiropteran bones and teeth suggested that the Central Ore Body cave was inhabited by bats. In modern caves, bat colonies can produce thick guano deposits unless underground water flushes them away. Pickford pointed directly to the possible role of guano—acidic and phosphate-rich—in the ore-forming chemistry. It is a vivid possibility: Berg Aukas descloizite, now prized in glass cases, may owe part of its story to a humid Miocene cave where bats lived above carbonate rocks and metal-bearing waters.
The locality is also part of primate paleontology. In 1992, Glenn Conroy, Martin Pickford, Brigitte Senut, John Van Couvering, and Pierre Mein described Otavipithecus namibiensis from Berg Aukas as the first known Miocene hominoid from the African continent south of equatorial East Africa. The holotype was a right mandibular corpus preserving teeth, found during exploration of karst-fill breccias in the Otavi region. The associated fauna indicated an age of about 13 ± 1 million years. For a mine known to collectors for black spear-point crystals, Berg Aukas also became a name in the history of southern African fossil apes.
The modern field story is less romantic. Environmental surveys in 2005 and 2007 documented the legacy of mining, roasting, smelting, slag, waste rock, and tailings. Researchers described an area of severe contamination roughly 3.5 km east-west by 2.5 km north-south, with unstable waste heaps, unsecured old galleries, tailings spilled into ephemeral streams, slag used in local roads, and dust hazards around the former processing area. One study noted that the hostel of the vocational school was moved to an uncontaminated area near Rietfontein after the results were presented. For collectors, that is part of the locality’s truth: the same orebody that produced some of the world’s finest descloizite also left behind a mine landscape requiring caution, respect, and remediation.
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