Lyonsite
Chemical formula: Cu<sup>2+</sup><sub>3</sub>Fe<sup>3+</sup><sub>4</sub>(V<sup>5+</sup>O<sub>4</sub>)<sub>6</sub>
Lyonsite is a rare copper and iron vanadate, forming tiny, black crystals with a metallic luster.
Properties
- Luster
- Metallic
- Streak
- Black
- Density
- 4.26
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Lyonsite is identified based on its unique occurrence environment – volcanic fumaroles. Identification is aided by its black color, strong metallic luster, and characteristic form of small, tabular crystals. Final confirmation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Distinguishing from Similar Minerals It can be confused with other black, metallic minerals found in fumaroles, such as hematite or some copper oxides. However, lyonsite is distinguished by its specific chemical composition (presence of vanadium, copper, and iron) and crystal habit. In field conditions, differentiation is practically impossible without appropriate equipment. ## Crystal Forms It forms very small, thin, tabular crystals with a hexagonal outline, often elongated and bladed. They occur as single flakes, rosette-like aggregates, or irregular aggregates on the lava surface.
Geological environment
## Genesis Lyonsite is a mineral of volcanic origin. It forms by sublimation from volcanic gases in high-temperature exhalative fumaroles. It crystallizes at temperatures between 600 and 800°C directly on the surface of volcanic rocks, such as basaltic andesites. ## Mineral Associations This mineral co-occurs with other fumarole minerals, such as shcherbinaite (V₂O₅), thenardite, hematite, as well as various sulfates and alkali metal halides. At the type locality (Izalco volcano), it was found in association with mcinnesite, howardevansite, bannermanite, and stoiberite. ## Localities The most important and well-documented occurrences of this rare mineral are: - Izalco volcano, Sonsonate department, El Salvador - type locality. - Fumaroles of Tolbachik volcano on the Kamchatka Peninsula, Russia.
Rarity
Very rare
For collectors
## Quality Criteria The collector's appeal of lyonsite primarily depends on the richness and aesthetics of microcrystal aggregates on the rock matrix. Specimens with well-formed, lustrous crystals forming dense aggregates are most valued. Due to their microscopic size, the quality of a specimen is assessed under magnification. The presence of rare associated minerals also increases the value of the specimen. ## Popular Localities The vast majority of specimens available on the collector's market come from the Tolbachik volcano in Kamchatka, Russia. Material from the type locality in El Salvador is extremely rare in collections.
Care and storage
## Cleaning Lyonsite specimens are usually very delicate and consist of microscopic crystals on a rock matrix. Mechanical or chemical cleaning is not recommended. If absolutely necessary, compressed air (from a safe distance) can be used to remove dust. ## What to Avoid Avoid contact with water, acids, and other chemicals. The crystals are brittle and susceptible to mechanical damage, so avoid vibrations, impacts, and abrasion. Do not subject it to ultrasonic cleaning. ## Storage Specimens should be stored in stable conditions, in a closed "micromount" container, to protect them from dust and physical damage. Avoid sudden changes in temperature and humidity.