Alflarsenite
Chemical formula: NaCa<sub>2</sub>Be<sub>3</sub>Si<sub>4</sub>O<sub>13</sub>(OH)·2H<sub>2</sub>O
Alflarsenite is an extremely rare beryllium, sodium, and calcium silicate, forming colorless, tabular crystals in nepheline-syenite pegmatites.
Description
## Characteristics Alflarsenite is a very rare mineral, visually presenting as colorless, transparent crystals with a tabular or lath-like habit. It typically forms small, fan-shaped or rosette-like aggregates, rarely exceeding a few millimeters in size. Due to its small size, it is a typical micromount mineral, requiring magnification for proper observation. ## Physical Properties This mineral is characterized by a Mohs hardness of 4, making it relatively soft. It has a vitreous luster and is transparent. Its calculated density is approximately 2.61 g/cm³. It exhibits perfect cleavage in one direction, which makes its crystals very delicate and susceptible to mechanical damage. ## Colors and Varieties Alflarsenite is a colorless mineral. No colored varieties or trade names are known. ## History and Name The mineral's name was given in honor of Alf Olav Larsen (born 1949), a Norwegian amateur mineralogist who discovered and described many new minerals from the Larvik area in Norway. Alflarsenite was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2008. ## Uses Due to its extreme rarity and small crystal size, alflarsenite has no industrial application. It is solely an object of scientific interest and a prized acquisition for advanced collections of rare and systematic minerals.
Diagnostic features
## Identification Amateur identification of alflarsenite is very difficult. Key indicators include its specific occurrence (cavities in nepheline-syenite pegmatites in the Larvik complex), the characteristic habit of thin-tabular crystals forming fan-shaped aggregates, and its association with other rare minerals. Definitive identification requires advanced analytical methods such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Distinguishing from Similar Minerals Alflarsenite can be confused with other colorless, tabular silicates found in the same environment, such as eudidymite or epididymite. Visual differentiation is practically impossible and relies on subtle differences in crystal shape that only an experienced specialist can discern. Final differentiation requires laboratory analysis. ## Crystal Forms Crystals are thin, tabular, with a rectangular or lath-like outline. They most often occur as radial, fan-shaped, or rosette-like clusters and aggregates growing on other minerals in rock cavities.
Geological environment
## Genesis Alflarsenite is a hydrothermal mineral. It forms in the late stage of nepheline-syenite pegmatite crystallization, crystallizing in miarolitic cavities (druses) from residual, rare-element-rich solutions. ## Mineral Associations This mineral coexists with a wide range of other pegmatitic minerals. The most common associations include aegirine, analcime, calcite, catapleiite, eudidymite, fluorite, gonnardite, natrolite, nepheline, petersenite-(Ce), polylithionite, and sodalite. ## Localities The only confirmed and most important occurrence of alflarsenite in the world is its type locality in Norway – the Larvik plutonic complex in the Vestfold region. The best specimens come from the AS Granit quarry (also known as Brudalen quarry) in Tvedalen.
Rarity
Extremely rare
Collector aspects
## Quality Criteria The quality of alflarsenite specimens, which are almost exclusively microminerals, is assessed based on several criteria. Specimens with sharp, well-formed, and undamaged crystals are most highly valued. The aesthetics of the aggregate are important – distinct, fully formed rosettes or fans are preferred. An attractive placement on the rock matrix and the presence of other rare, well-crystallized associated minerals are additional advantages. ## Popular Localities The only source of collectible alflarsenite specimens is its type locality – the quarries within the Larvik syenite complex in Norway. Specimens from this location are considered the best in the world.
Care and storage
## Cleaning Alflarsenite specimens are extremely delicate and must be handled with the utmost care. A photographic air blower is best for removing dust. Any mechanical contact, including with a soft brush, risks damaging the fragile crystals. Washing in water is not recommended due to the risk of damaging the aggregates. ## What to Avoid Ultrasonic cleaners, all chemical agents, acids, and detergents must be absolutely avoided. The mineral is sensitive to shocks and impacts due to its perfect cleavage. It should be protected from dust and sudden temperature changes. ## Storage Alflarsenite should be stored exclusively in specialized micromineral boxes (micromounts), which protect it from physical damage, dust, and moisture. It is not suitable for display outside of such protection.