Beaverite-(Zn)
Chemical formula: Pb<sup>2+</sup>Zn<sup>2+</sup>Fe<sup>3+</sup><sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>(OH)<sub>6</sub>
Beaverite-(Zn) is a rare secondary mineral of the alunite group, forming characteristic, bright yellow coatings and microscopic crystals.
Description
## Characteristics Beaverite-(Zn) is a lead, zinc, and iron sulfate belonging to the alunite supergroup. It most commonly occurs as earthy, powdery, or massive coatings and crusts on other minerals. Less frequently, it forms aggregates of very small, platy crystals with a hexagonal outline, visible only under magnification. Its most characteristic feature is an intense, canary yellow color, which can transition to yellowish-brown or greenish-yellow hues. ## Physical Properties It is a relatively soft and brittle mineral. The luster is described as dull, earthy, and in the case of more massive aggregates, waxy. In mass, it is opaque, and only on thin edges or in the case of microcrystals can it be translucent. Its calculated density is approximately 4.35 g/cm³. ## Colors and Varieties This mineral does not form color varieties or commercial forms. Its coloration is constant and related to its chemical composition, oscillating around various shades of yellow. It is the zinc analog of beaverite-(Cu), in which copper has been replaced by zinc. ## History and Name The name refers to its chemical composition – it is the zinc (Zn) end-member of the series with beaverite-(Cu). The original beaverite was named in 1911 after its discovery locality in Beaver County, Utah, USA. The species Beaverite-(Zn) was formally separated and approved by the International Mineralogical Association (IMA) in 2006 as part of the revision of the alunite supergroup systematics. ## Uses Beaverite-(Zn) has no industrial applications. It is of purely scientific and collector interest.
Diagnostic features
## Identification Key diagnostic features include: bright yellow color, earthy or dull appearance, occurrence as coatings, and geological environment. Beaverite-(Zn) is a secondary mineral, found in the oxidation zones of ore deposits. ## Distinguishing from Similar Minerals It can be confused with other yellow secondary minerals. From jarosite, with which it often co-occurs, it is difficult to distinguish without chemical analysis. It differs from pyromorphite, which usually forms better-developed, lustrous crystals with a hexagonal or dodecahedral habit. From bindheimite, it is distinguished by the presence of sulfates in its composition. Certain identification almost always requires advanced studies, e.g., EDS spectroscopy. ## Crystal Forms Most commonly found as earthy and powdery masses. Well-formed crystals are rare, appearing as microscopic, hexagonal plates gathered in rosette-like or radial aggregates.
Geological environment
## Genesis Beaverite-(Zn) is a secondary mineral that forms in the oxidation zones (so-called iron caps) of polymetallic sulfide deposits. It results from the weathering of primary minerals containing lead, zinc, iron, and sulfur, under low pH conditions. ## Mineral Associations It often co-occurs with other secondary minerals of the oxidation zone, such as anglesite, cerussite, smithsonite, hemimorphite, goethite, jarosite, as well as with quartz and clay minerals. ## Localities The most important and typical locality for beaverite-(Zn) is the Tsumeb mine in Namibia, from which the best-known specimens originate. It is also found in the historical locality for beaverite-(Cu) in Beaver County (Utah, USA) and in several other places worldwide, including Greece (Lavrion mines) and Australia.
Rarity
Very rare
Collector aspects
## Quality Criteria The quality of collector specimens primarily depends on the intensity and purity of the yellow color and the richness of the coating on the rock matrix. Samples with visible, even under a microscope, aggregates of small crystals are exceptionally valued. Association with other rare or well-formed minerals, especially from Tsumeb, also enhances its attractiveness. ## Popular Localities Specimens from the Tsumeb mine in Namibia are by far the most valued by collectors. This locality is famous for its exceptional oxidation zone mineralogy, and beaverite-(Zn) is one of many rare minerals found there.
Care and storage
## Cleaning Specimens should be cleaned very carefully, preferably dry, using a soft brush or a photographic air blower to remove dust. Contact with water should be minimized; if necessary, distilled water can be used, and the specimen should be immediately and thoroughly dried. ## What to Avoid The mineral is soft and brittle, so all impacts, scratches, and vibrations should be avoided. Cleaning in ultrasonic cleaners is not recommended. It should be protected from contact with acids and other aggressive chemicals. ## Storage It is recommended to store specimens in separate, sealed boxes (e.g., micromount type), which protects them from dust, light, and mechanical damage. A label with the name and locality is crucial for preserving scientific and collector value.