Wickenburgite
Chemical formula: Pb<sup>2+</sup><sub>3</sub>CaAl<sub>2</sub>Si<sub>10</sub>O<sub>27</sub>·4H<sub>2</sub>O
Wickenburgite is a rare, hydrated lead calcium aluminum silicate, forming colorless or white, tabular crystals with a pearly luster.
Properties
- Mohs hardness
- 3.5
- Luster
- Pearly
- Streak
- White
- Density
- 3.45
- Cleavage
- Perfect on {0001}
- Fracture
- Uneven
- Transparency
- Transparent to Translucent
- Crystal system
- Trigonal
Diagnostic features
## Identification Characteristic features of wickenburgite include its forms of occurrence – thin, tabular crystals forming radial aggregates or rosettes. A pearly luster on cleavage planes, white color, and co-occurrence with other rare lead minerals are also important diagnostic clues. ## Distinguishing from Similar Minerals Wickenburgite can be confused with other white, tabular silicates or sulfates, such as gypsum or barite, but differs from them in hardness and paragenesis. It is distinguished from hydrocerussite by its lack of reaction with hydrochloric acid. Final confirmation requires advanced analytical methods, such as X-ray diffraction (XRD). ## Crystal Forms Crystals are tabular, flattened parallel to the {001} plane, and have a pseudohexagonal outline. They typically occur as radial or rosette aggregates, as well as thin veins and crusts.
Geological environment
## Genesis Wickenburgite is a secondary mineral, forming in the oxidation zones of polymetallic deposits, especially those rich in lead. It forms under low-temperature conditions in voids and fissures in rocks, often in the presence of other secondary lead minerals. ## Mineral Associations This mineral often co-occurs with other rare secondary minerals. In the type locality (Potter-Cramer mine, Arizona), it was found in association with minerals such as cerussite, anglesite, phosgenite, dioptase, wulfenite, mimetite, as well as rarer ones: shattuckite, willemite, hydrocerussite, and fornacite. ## Localities The most important and classic occurrence of wickenburgite is its type locality – the Potter-Cramer mine near Wickenburg, Arizona, USA. It is also known from several other locations worldwide, including the Touissit mine in Morocco and the Clara mine in the Black Forest, Germany. All these localities are oxidation zones of ore deposits.
Rarity
Very rare
For collectors
## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp crystals forming aesthetic, radial aggregates or rosettes. Contrast with the rock matrix and absence of damage are important. Crystal size is crucial – specimens with larger, well-defined tablets command higher prices. Purity of color (snow-white) also increases the specimen's value. ## Popular Localities By far the most desirable and classic specimens come from the type locality in Arizona (Potter-Cramer mine). They are considered exemplary for this mineral species.
Care and storage
## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Distilled water is permissible, but prolonged soaking should be avoided. Always thoroughly dry the specimen after cleaning. ## What to Avoid Avoid contact with acids and other chemicals that can damage the mineral. Due to its low hardness, it is susceptible to scratches and mechanical damage. It should not be cleaned with ultrasound. Protect it from high temperatures. ## Storage Wickenburgite specimens, being fragile and often small, are best stored in enclosed display boxes, separated from harder minerals. Protect from dust and direct sunlight.