Overview

Descloizite is a lead–zinc vanadate, PbZn(VO4)(OH), best known for striking, lustrous blades and rosette clusters in colors ranging from black to deep brown with glowing red to orange “root beer” translucence on thin edges. It forms in the oxidized zones of Pb–Zn deposits and often associates with wulfenite, mimetite, vanadinite, calcite/dolomite, smithsonite, and mottramite (its Cu-analogue and solid-solution partner). Classic specimens feature sharp, highly lustrous bladed crystals in sprays or bow-tie rosettes, perched on pale carbonate matrix for dramatic contrast. The finest examples come from the Otavi Mountainland in Namibia (Tsumeb, Berg Aukas, Guchab), and from Mexico’s Ojuela Mine, with aesthetics ranging from elegant jackstraw networks to sculptural, jet-black rosettes that glow warm red when backlit. Although not a “gem” species, exceptional luster, form, and contrast elevate descloizite to centerpiece status in many display cases.

Popularity

Descloizite has long delighted collectors who appreciate dark, lustrous species with superb crystal form. Its heyday coincides with mining eras at Tsumeb and satellite Otavi deposits, and with repeated discoveries at Ojuela in Mexico. Demand is driven by:

• Aesthetics: glossy, razor-sharp blades in attractive rosettes and sprays; strong matrix contrast.
• Translucence: “cognac” to cherry-brown glow at the edges under strong light adds life to the dark color.
• History and provenance: Tsumeb and Berg Aukas pedigrees command premiums; Ojuela continues to supply excellent, more affordable pieces.
• Variety: from snow-white dolomite with black rosettes (Namibia) to rich brown sprays on limonite with wulfenite (Mexico).

While cabinet masterpieces from classic pockets are scarce and pricey, fine small cabinet and miniature pieces remain accessible. Collectors also appreciate the mottramite–descloizite solid solution, which invites nuanced study of zoning, color, and locality signatures.

Top Collecting Localities

Berg Aukas Mine, Namibia

Berg Aukas produced elegant jackstraw bundles and rosettes of descloizite with excellent luster and sharp terminations, frequently on pale dolomite or calcite for striking contrast. The aesthetic hallmark is the combination of glossy, finely bladed crystals forming sculptural sprays or bow-ties on bright matrix. Although many specimens appear black at first glance, backlighting reveals reddish to cognac tones along edges. Associations may include mimetite, smithsonite, cerussite, or mottramite. Berg Aukas pieces are prized for their balance and composition—often exceptionally “clean” and display-ready—making them among the most coveted Namibian descloizites after Tsumeb.

Collector’s Guide

Evaluating Specimen Quality

• Color and translucence:

  • Most descloizite appears black to very dark brown; look for “cognac” to cherry-brown translucence along thin edges when strongly backlit—this gives life to the crystals and is a plus.
  • Overall hue can range from chocolate-brown to sooty black; rich brown edges and warm internal glow are especially prized from Tsumeb and Berg Aukas.

• Luster:

  • Top pieces exhibit bright, sub-adamantine to resinous luster with crisp reflections on the blade faces. A satiny or dull surface reduces impact unless compensated by exceptional size or aesthetics.

• Crystal form and size:

  • Descloizite is famed for sharp bladed crystals forming rosettes, bow-ties, and sprays. Symmetry and definition of individual blades matter.
  • Large, thick, undamaged blades or rosettes are scarce; most fine crystals range from a few millimeters to 1–2 cm. Larger, well-formed crystals carry strong premiums.

• Aesthetics and matrix:

  • The best pieces balance strong contrast (black crystals on white dolomite/calcite) with elegant composition—clusters positioned upright, with depth and a clean silhouette.
  • Attractive associations include wulfenite (Ojuela), mimetite, smithsonite, calcite/dolomite. Complementary color adds appeal and value.

• Condition:

  • Blade edges are fragile. Inspect terminations carefully for nicks; damage is common on rosette tips and along the periphery of sprays.
  • Porous gossan matrices (Ojuela) can shed grit; tight, solid matrix with firmly attached crystals is preferred.
  • As always, minimal or no damage on the main display surface is ideal; a single small bruise on a peripheral crystal is usually acceptable on highly aesthetic pieces.

• Locality and provenance:

  • Tsumeb and Berg Aukas command premiums for pedigree, luster, and form. Guchab pieces with striking black-on-white contrast are especially desirable. Ojuela offers breadth and iconic associations, with top cabinets still strongly valued.

• Descloizite vs. mottramite (solid solution):

  • Many crystals lie in the descloizite–mottramite series. Greenish to olive tones and lower translucence suggest mottramite-rich compositions, while deep brown to black with warm brown translucence typically indicates descloizite-rich. Only analysis (EDS/Raman) is definitive; reputable labels and locality context help.

Detecting Repairs or Treatments

• Repairs:

  • Re-attachments can occur where rosettes detached from matrix or where fragile blades broke during extraction.
  • Examine bases of clusters and along perfect plane-like seams for epoxy. A loupe and low-angle light help; some epoxies show faint fluorescence under LW-UV.
  • Porous Ojuela gossan is sometimes consolidated with thin adhesives; look for subtle darkening or a “sealed” look in the matrix around crystal bases. Professional, disclosed stabilization is often acceptable on otherwise superb pieces.

• Treatments:

  • Color/heat treatments are essentially unknown for descloizite specimens.
  • Cleaning often involves iron-stain removers on matrix; avoid pieces showing etched or dulled carbonate where over-aggressive prep may have occurred. Always ask dealers about preparation history.

Care and Storage

Descloizite is relatively soft and brittle (Mohs ~3–3.5; high density; brittle tenacity), with thin-bladed crystals prone to edge chipping.

• Handling:

  • Support the matrix; avoid touching rosette tips or blade edges. Use two hands for larger specimens.
  • For porous Ojuela gossan, cradle the base firmly to prevent granular shedding.

• Cleaning:

  • Best is gentle air bulb or very soft brush to remove dust. If necessary, use distilled water with a drop of mild soap and a soft brush—avoid soaking fragile gossan matrices and avoid any ultrasonic or steam cleaning.
  • Do not use acids: many matrices are carbonate (calcite/dolomite) and will etch. Iron-stain removers can be safe with care on matrix but test on an inconspicuous spot first.

• Light and temperature:

  • Colors are generally stable; normal display lighting is fine. Avoid prolonged, intense heat or rapid temperature swings that could stress blades or adhesives used in stabilization.

• Storage:

  • Provide cushioned, compartmentalized storage so no specimen touches another. Keep away from harder species that could scratch it.
  • Secure in display with a small amount of museum putty on the matrix (not on crystal edges).

• Safety:

  • Descloizite is a lead–vanadium mineral. While stable under normal handling, avoid inhaling dust or ingesting particles. Wash hands after handling; keep away from children and pets; do not lick specimens.

With thoughtful selection and gentle care, descloizite offers superb aesthetics—jet-black brilliance, elegant crystal architecture, and a warm internal glow that makes the finest pieces unforgettable.