Alexearlite
Chemical formula: Hg<sup>2+</sup><sub>3</sub>(Mo<sup>6+</sup>O<sub>4</sub>)S<sup>2-</sup><sub>2</sub>
An extremely rare mercury molybdate sulfate, forming microscopic, acicular crystals of an intense orange-yellow color.
Description
## Characteristics Alexearlite is a mineral from the sulfate-molybdate group, visually appearing as aggregates or druses of small, acicular or prismatic crystals. Individual crystals rarely exceed 0.1 mm in length, forming a delicate, sparkling coating on the surface of the host rock. Its most characteristic feature is its vivid orange-yellow to yellowish-orange color, which distinguishes it in its natural environment. ## Physical Properties This mineral is characterized by a strong, adamantine luster. It is transparent to translucent. Due to the microscopic size of the crystals, hardness has not been precisely determined. The density calculated based on chemical composition and crystal structure is 8.15 g/cm³. ## Colors and Varieties Alexearlite occurs in a uniform range of colors, from yellowish-orange to orange-yellow. No color varieties or commercial varieties are known. ## History and Name The mineral was first described in 1999 by W. W. Pinch, W. I. L. H. M. van der Sluis, and R. S. W. M. van der Sluis. Its name honors Alex V. G. E. Arnold (born 1947), a mineral collector from Arizona, who discovered the first specimens of this mineral. The type locality is the B&B Mine in La Paz County, Arizona, USA. ## Uses Due to its extreme rarity and occurrence in the form of microscopic crystals, alexearlite has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized micromount mineral collectors.
Diagnostic features
## Identification Field identification of alexearlite is practically impossible without specialized equipment. In laboratory conditions, it is recognized based on a combination of features: orange-yellow color, acicular crystal habit, adamantine luster, and unique chemical composition, confirmed by methods such as energy-dispersive spectroscopy (EDS). Its locality and associated minerals are also crucial. ## Differentiation from Similar Minerals Alexearlite can be confused with other fine-grained, colorful secondary minerals, especially wulfenite, which often occurs in the same locality. However, wulfenite typically forms tabular or pyramidal crystals, in contrast to acicular alexearlite. Final differentiation requires chemical analysis. ## Crystal Forms It forms druses and aggregates composed of very small, acicular or elongated prismatic crystals, reaching up to 0.1 mm in length.
Geological environment
## Genesis Alexearlite is a very rare secondary mineral. It forms in the oxidation zone of epithermal, polymetallic mercury-bearing deposits, which are hosted in volcanic rocks. ## Mineral Associations At the type locality (B&B Mine, Arizona), alexearlite occurs in association with wulfenite, mimetite, cerussite, quartz, calcite, and iron oxides. ## Localities The only confirmed occurrence of this mineral in the world is its type locality – the B&B Mine in the Little Horn Mountains, La Paz County, Arizona, USA.
Rarity
Extremely rare
Collector aspects
## Quality Criteria As a micromount mineral, the collector's value of an alexearlite specimen depends on several factors. Specimens with rich, dense aggregates of intensely colored crystals are most highly prized. The aesthetics of the matrix and the presence of well-formed crystals of associated minerals, such as wulfenite, are also important. ## Popular Localities All known collector specimens come from a single location in the world – the B&B Mine in Arizona, USA. This is therefore a crucial locality for obtaining this mineral.
Care and storage
## Cleaning Alexearlite specimens are extremely delicate. For dust removal, only careful use of a photographic blower or other source of a gentle air stream is recommended. All wet cleaning, including with water or ultrasonics, should be avoided. ## What to Avoid The mineral is susceptible to mechanical damage, shocks, and abrasion. Contact with all chemicals should be avoided. As a mercury-containing mineral, it should be handled with caution – avoid inhaling dust and store it in a closed container. ## Storage The safest form of storage is a sealed "micromount" box, which protects the specimen from dust, physical damage, and limits potential mercury vapor emission. It should be kept in stable conditions, away from vibrations.