Alfredopetrovite
Chemical formula: Al<sub>2</sub>(Se<sup>4+</sup>O<sub>3</sub>)<sub>3</sub>·6H<sub>2</sub>O
Alfredopetrovite is a very rare, hydrated aluminum selenite, forming tiny, acicular crystals on rock druses.
Description
## Characteristics Alfredopetrovite is a mineral from the selenite group, and chemically a hydrated aluminum selenite. It most often forms colorless or white, very small crystals with an acicular or platy habit. These crystals usually occur as radial aggregates, rosettes, or chaotically arranged felt-like masses, growing on the host rock. Due to the small size of the crystals, specimens are most often viewed under magnification. ## Physical Properties This mineral is very soft, with a Mohs hardness of approximately 2.5. It exhibits a vitreous luster and is transparent to translucent. It is a brittle and delicate mineral. ## Colors and Varieties Alfredopetrovite is typically colorless or white. No colored varieties or trade names are known. ## History and Name The mineral was officially recognized by the International Mineralogical Association (IMA) in 2015. Its name honors Alfredo Petrov (born 1945), an American chemist, mineral collector, and specialist in Bolivian mineralogy, who first drew attention to the unusual selenite parageneses in the El Dragón mine. The type locality and only known occurrence of this mineral is the El Dragón mine in Bolivia. ## Uses Alfredopetrovite, as an extremely rare mineral occurring in microscopic quantities, has no industrial application. It is solely an object of scientific interest and a prized acquisition for specialized collectors of rare minerals.
Diagnostic features
## Identification Identification of alfredopetrovite is primarily based on its unique locality (El Dragón mine), characteristic habit of radial aggregates of white, acicular crystals, and co-occurrence with other rare selenites. Positive identification requires advanced analytical methods such as energy-dispersive spectroscopy (EDS) or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Alfredopetrovite can be confused with other white, acicular secondary minerals. It is distinguished from co-occurring olsacherite (a sulfate) at the same locality by its chemical composition. It may resemble some zeolites, but the geological context (selenium-rich environment) is a key diagnostic clue. ## Crystal Forms Crystals are acicular or platy, very fine. They typically form radial, spherical aggregates, rosettes, or tangled masses on the surface of the host rock (most often on sandstone).
Geological environment
## Genesis Alfredopetrovite is a secondary mineral, formed in the oxidation zone of hydrothermal selenium deposits. It forms as a result of the weathering of primary selenium minerals and the reaction of selenium-rich solutions with aluminum-containing minerals. ## Mineral Associations This mineral occurs in association with other, often very rare, selenite and sulfate minerals. The most common associated minerals are native selenium, mandarinoite, ahlfeldite, penroseite, and olsacherite. The entire paragenesis occurs on a sandstone matrix. ## Localities The only known worldwide locality for alfredopetrovite is the El Dragón mine, in Antonio Quijarro Province, Potosí Department, Bolivia.
Rarity
Extremely rare
Collector aspects
## Quality Criteria The most highly valued specimens are those with rich, dense coverage of radial alfredopetrovite aggregates on the smallest possible rock matrix. The aesthetics of the aggregates, their size, and the absence of damage are important. Specimens with visible, well-formed crystals of other rare associated minerals, especially native selenium or colorful mandarinoite, add additional value. ## Popular Localities For collectors, the only source of specimens is the type locality – the El Dragón mine in Bolivia. Specimens from this location are considered classic and highly desirable in specialized collections.
Care and storage
## Cleaning The mineral is extremely delicate and potentially sensitive to water. Cleaning should only be done dry, using a very soft brush to remove dust or a gentle stream of compressed air. Any contact with water and cleaning fluids should be avoided. ## What to Avoid Water, ultrasonic cleaners, all chemicals, high temperatures, and sudden temperature changes must be absolutely avoided. The mineral is very soft and brittle, making it susceptible to mechanical damage. It should be protected from shocks and impacts. ## Storage It is recommended to store specimens in closed, padded "micromount" boxes, which protect against dust, moisture, and physical damage. Display should be in stable conditions, away from direct sunlight and heat sources.