Davidlloydite
Chemical formula: Zn<sup>2+</sup><sub>3</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>·4H<sub>2</sub>O
Davidlloydite is a very rare, hydrated zinc arsenate, forming characteristic pale pink or lilac coatings and aggregates of tiny crystals.
Properties
- Mohs hardness
- 3
- Luster
- Vitreous
- Streak
- White
- Density
- 3.85
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification The key features allowing the identification of davidlloydite are its unique pale pink or lilac color, occurrence in the form of fine-grained coatings, and origin from a specific geological environment – the oxidation zone of ores in the Tsumeb mine. ## Distinguishing from Similar Minerals Davidlloydite is sometimes confused with other pink arsenates. Erythrite (cobalt bloom) usually has a much more intense, crimson or magenta color. Köttigite, also a zinc arsenate, can have a similar hue, but is more often reddish-pink and forms crystals of a different habit. Final differentiation requires advanced analytical methods, such as chemical composition analysis. ## Crystal Forms This mineral forms drusy aggregates, radial aggregates, or coatings composed of very small (usually less than 1 mm), flattened, platy or acicular crystals.
Geological environment
## Genesis Davidlloydite is a secondary mineral, formed in the oxidation zone of hydrothermal, polymetallic ore deposits. It forms in voids and fissures within heavily weathered ores containing tennantite, as a result of the weathering processes of primary zinc and arsenic minerals. ## Mineral Associations This mineral occurs in association with other rare, secondary arsenates, such as legrandite, köttigite, adamite, warikahnite, and the zinc variety of olivenite. It also co-occurs with smithsonite and tennantite. ## Localities The only confirmed and significant occurrence of davidlloydite in the world is its type locality – the Tsumeb mine in the Otjikoto region of Namibia. This is one of the most famous mineralogical sites on Earth, known for its extraordinary diversity and quality of secondary minerals.
Rarity
Very rare
For collectors
## Quality Criteria The most highly valued davidlloydite specimens are characterized by rich, extensive coatings with an intense, evenly distributed pink color. Although the crystals are always small, those that show a distinct shape and luster are more desirable. Aesthetic association with other rare and well-formed associated minerals, such as legrandite or adamite, also adds significant value. ## Popular Localities For collectors, the only source of davidlloydite specimens is historical material from the Tsumeb mine in Namibia, which is now closed. This means that new specimens do not appear on the market, and available examples come exclusively from old collections.
Care and storage
## Cleaning Davidlloydite specimens are very delicate and should be handled with the utmost care. For dust removal, it is best to use a photographic air blower or a can of compressed air, held at a safe distance. If necessary, the specimen can be very carefully rinsed in distilled water using an exceptionally soft brush, minimizing contact with water. ## What to Avoid Ultrasonic cleaners, strong jets of water, and all chemical agents, especially acids, should be strictly avoided. As a hydrated mineral, it is sensitive to high temperatures, which can lead to its permanent damage. It should also be remembered that as an arsenate, it is a toxic mineral – hands should be thoroughly washed after each contact with the specimen. ## Storage It is recommended to store specimens in closed, stable containers or display cases to protect them from dust, mechanical damage, and sudden changes in humidity. Exposure to direct sunlight should be avoided, as it could theoretically cause its delicate color to fade.