Pellouxite
Chemical formula: (Cu<sup>1+</sup>,Ag<sup>1+</sup>)<sub>2</sub>Pb<sup>2+</sup><sub>21</sub>Sb<sup>3+</sup><sub>23</sub>S<sup>2-</sup><sub>55</sub>ClO
Pellouxite is a very rare lead-antimony sulfosalt with chlorine, forming acicular crystals with a metallic luster.
Properties
- Mohs hardness
- 2
- Luster
- Metallic
- Streak
- Black
- Density
- 6.13
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Monoclinic
Diagnostic features
## Identification Pellouxite is identified by its unique form – very thin, acicular or hair-like crystals with a metallic luster, gathered in tangled aggregates. Its dark gray color and occurrence in a specific geological environment are key indicators. However, definitive identification requires advanced analytical methods, such as X-ray microanalysis (EDS/WDS). ## Distinguishing from Similar Minerals Pellouxite can be confused with other acicular sulfosalts, such as jamesonite, boulangerite, or zinkenite. Distinguishing it with the naked eye or under a microscope is practically impossible without chemical analysis. Pellouxite is characterized by a unique combination of elements: lead, antimony, copper, silver, and chlorine. ## Crystal Forms This mineral exclusively forms very fine, acicular or hair-like crystals, often bent and tangled into woolly or felt-like aggregates. The crystals are elongated along the [001] axis.
Geological environment
## Genesis Pellouxite forms as a result of hydrothermal processes in the final stages of crystallization. It occurs in small vugs and fissures in metamorphic rocks, such as dolomitic marbles, that have been subjected to hydrothermal solutions. ## Mineral Associations This mineral co-occurs with other, often rare, hydrothermal minerals. In its type locality (Buca della Vena), it was found in association with sphalerite, pyrite, quartz, dolomite, as well as rarer minerals such as rouxelite, moëloite, laffittite, and other sulfosalts. ## Localities The only confirmed and described locality for pellouxite in the world is its discovery site – the Buca della Vena mine, located in the municipality of Stazzema, in the Apuan Alps, Tuscany, Italy.
Rarity
Extremely rare
For collectors
## Quality Criteria For collectors, the most important criterion is the richness and visibility of pellouxite aggregates on the rock matrix. Since the crystals are microscopic, specimens are evaluated under a microscope. The most desirable specimens are those that show dense, tangled clusters of acicular crystals, preferably accompanied by other well-formed, rare minerals. Contrast with a light matrix (e.g., quartz or dolomite) also enhances visual value. ## Popular Localities The only source of pellouxite specimens is the Buca della Vena mine in Italy. This is a classic locality for many rare sulfosalts, and specimens from there are highly prized by specialized collectors.
Care and storage
## Cleaning Due to its extreme delicacy and reactivity, cleaning pellouxite is highly inadvisable. Any attempts at mechanical or chemical cleaning may irreversibly damage the specimen. It should be left undisturbed on its original rock matrix. ## What to Avoid Avoid contact with water, chemicals, and sudden temperature changes. The crystals are very brittle and flexible, so any touching or vibrations should be avoided. Prolonged exposure to air and humidity can lead to oxidation and slow decomposition of the mineral. ## Storage Pellouxite specimens should be stored only under stable conditions, preferably in a tightly sealed, padded "micromount" box, away from light, moisture, and chemical contaminants. Storage in a dry environment, for example with the use of silica gel, is recommended.