Cassedanneite
Chemical formula: Pb<sup>2+</sup><sub>5</sub>(V<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>(Cr<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>·H<sub>2</sub>O
Cassedanneite is a rare, hydrated lead vanadate and chromate, forming aggregates of microscopic, orange-red crystals.
Properties
- Mohs hardness
- 3.5
- Luster
- Resinous to adamantine
- Streak
- Orange
- Density
- 6.0-6.2
- Cleavage
- Good on {010}
- Fracture
- Uneven
- Transparency
- Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification Cassedanneite is identified by its characteristic, intense orange-red color, its occurrence as small, rosette-like aggregates, and its distinctive resinous luster. Its origin is also key – it occurs in the oxidation zones of lead deposits alongside other chromates and vanadates. ## Distinguishing from Similar Minerals This mineral can be confused with other secondary lead minerals of similar color, such as wulfenite, crocoite, or vanadinite. - **Crocoite** (PbCrO₄) typically forms larger, better-formed, prismatic crystals of a bright red color. - **Vanadinite** (Pb₅(VO₄)₃Cl) crystallizes in the hexagonal system, forming characteristic hexagonal, prismatic, or tabular crystals. - **Wulfenite** (PbMoO₄) most often forms thin, square tabular crystals and has a yellow streak (cassedanneite's streak is orange). Final differentiation often requires advanced analytical methods (e.g., EDS). ## Crystal Forms Cassedanneite forms very small, thin, tabular or platy crystals, often flattened. They typically occur as radial or rosette aggregates, as well as crusts and coatings.
Geological environment
## Genesis Cassedanneite is a secondary mineral, formed in the oxidation zones (so-called iron caps) of lead ore deposits. Its crystallization requires specific geochemical conditions – the simultaneous presence of mobile lead, vanadium, and chromium in hydrothermal solutions. ## Mineral Associations This mineral co-occurs with other secondary lead minerals. In its type locality (Brazil), it was found in association with anglesite, cerussite, chervetite, duftite, heterosite, mimetite, pyromorphite, vanadinite, and wulfenite. ## Localities The most important and type locality for cassedanneite is the Berezovsk (Berezovskoe) lead mine in the Sverdlovsk Oblast, Ural Mountains, Russia. The mineral has also been confirmed in the Preguiça mine in Sobral da Adiça, Portugal, and in several locations in Germany (including Bad Ems).
Rarity
Very rare
For collectors
## Quality Criteria The collector's appeal of a cassedanneite specimen depends on several factors. Highly valued specimens are those with rich, dense aggregates of well-formed, though still microscopic, crystals. The intensity and saturation of the orange-red color also play a crucial role. Contrast with the rock matrix and the presence of associated minerals that form aesthetic compositions are important. Due to their microscopic nature, specimens are evaluated under magnification. ## Popular Localities Specimens from the type locality – the Berezovsk mine in the Ural Mountains, Russia – are by far the most valued and sought after by collectors. The best known examples of this mineral originate from there.
Care and storage
## Cleaning Specimens should be cleaned very carefully, using compressed air to remove dust. Any contact with water or chemicals is inadvisable. Due to the microscopic size of the crystals, mechanical cleaning (e.g., with a brush) will almost certainly damage them. ## What to Avoid Avoid contact with water, acids, and other chemicals. The mineral is sensitive to shock and abrasion. It should not be heated or exposed to prolonged strong light. ## Storage Cassedanneite specimens should be stored in sealed, stable containers (so-called "micromount boxes") to protect them from dust, humidity, and mechanical damage. Due to the lead and chromium content, hands should be washed after handling the mineral.