Cesàrolite
Chemical formula: Pb<sup>2+</sup>Mn<sup>4+</sup><sub>3</sub>O<sub>6</sub>(OH)<sub>2</sub>
Cesàrolite is a rare, secondary lead and manganese oxide mineral, forming characteristic black, earthy, or fibrous coatings and aggregates.
Properties
- Mohs hardness
- 3
- Luster
- Dull
- Streak
- Black-brown
- Density
- 4.65
- Cleavage
- Perfect on {0001}
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Trigonal
Diagnostic features
## Identification Cesàrolite is identified by its characteristic mode of occurrence – black, sooty or earthy coatings and crusts on other minerals, especially in the oxidation zones of ore deposits. Its steel-gray to black color, dull luster, and low hardness are key features. It produces a black-brown streak. ## Distinguishing from Similar Minerals It can be confused with other manganese oxides, such as pyrolusite, hollandite, or romanechite. Differentiation often requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS). In field conditions, distinguishing it from other "black manganese oxides" is practically impossible without knowledge of the mineral association typical for a given locality. ## Crystal Forms Cesàrolite crystals are microscopic and take the form of hexagonal plates or flakes. They typically form dense, felted masses, earthy coatings, or very fine, fibrous aggregates.
Geological environment
## Genesis Cesàrolite is a secondary mineral, formed in the oxidation zones (so-called gossans) of lead and manganese ore deposits. It forms as a result of weathering and alteration of primary minerals containing these elements, such as galena and manganese minerals, under low temperature and pressure conditions, close to the Earth's surface. ## Mineral Associations It often co-occurs with other secondary minerals of the oxidation zone. Typical associated minerals include cerussite, anglesite, coronadite, pyromorphite, as well as various manganese oxides (hollandite, pyrolusite) and iron oxides (goethite, hematite). ## Localities Key localities for this rare mineral include Sidi Amor ben Salem in Tunisia (type locality); Furnace mine in Pima County, Arizona (USA); Red Gill mine in Cumbria (United Kingdom); Broken Hill in New South Wales (Australia); and deposits in the Laurion region in Greece.
Rarity
Rare
For collectors
## Quality Criteria The collector appeal of cesàrolite primarily depends on the richness and aesthetics of the coating or aggregate on the host rock. Specimens with well-formed, though still microscopic, fibrous aggregates or those that form a distinct, thick coating of intense black color are most valued. Contrast with a lighter substrate mineral (e.g., cerussite) also enhances the visual appeal of the specimen. Due to its rarity, even small but well-identified samples are sought after. ## Popular Localities Specimens from classic localities, such as Tunisia, Arizona (USA), or Laurion (Greece), are most desired by collectors due to their historical significance and material quality.
Care and storage
## Cleaning Cesàrolite specimens are extremely delicate and brittle. Mechanical cleaning should be avoided. If absolutely necessary, a very soft brush can be used to remove loose dust. Water or any liquids should not be used, as they can damage earthy or fibrous aggregates. ## What to Avoid Contact with water, chemicals (especially acids), ultrasound, and any vibrations or impacts must be strictly avoided. The mineral is very soft and easily abraded or disintegrated. It should not be heated or exposed to sudden temperature changes. ## Storage It is recommended to store specimens in tightly sealed "micromount" boxes, away from dust, moisture, and vibrations. It is best to display it in its original box to minimize the risk of damage during handling.