Markhininite
Chemical formula: Tl<sup>1+</sup>Bi<sup>3+</sup>(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>
Markhinite is a colorless, transparent thallium bismuth sulfate, occurring as microscopic crystals in volcanic exhalations.
Description
## Characteristics Markhinite is a thallium bismuth sulfate, forming colorless and transparent crystals. It typically occurs as very small, short prisms, not exceeding 0.2 mm in length. These crystals often form radial aggregates or thin, crystalline crusts on the surface of the host rock. Due to the small size of the crystals, a microscope is necessary for their observation. ## Physical Properties The mineral is characterized by a vitreous luster. It is transparent. Its density, calculated based on the chemical formula and unit cell parameters, is 5.93 g/cm³. Hardness has not been determined. ## Colors and Varieties Markhinite is colorless. No colored varieties or trade names are known. ## History and Name The mineral was named in honor of Evgeny Konstantinovich Markhinin (1926–2012), a Russian volcanologist who made significant contributions to the study of volcanism, particularly in the Kuril Islands and Kamchatka. The mineral was officially approved by the International Mineralogical Association (IMA) in 2018 under number IMA2018-019. The type locality is the Arsenatnaya fumarole on Tolbachik volcano. ## Applications Markhinite has no industrial applications. It is solely an object of scientific research and a valuable acquisition for specialized collectors of rare minerals and microminerals, mainly due to its unique chemical composition and origin.
Diagnostic features
## Identification Identifying markhinite based on visual characteristics is practically impossible due to its microscopic size and lack of distinctive macroscopic features. Reliable identification requires advanced analytical methods, such as electron microprobe (EDS/WDS) to determine chemical composition or X-ray diffraction (XRD) for crystal structure analysis. A key diagnostic clue is its occurrence in the specific environment of volcanic fumaroles on Tolbachik volcano. ## Distinguishing from Similar Minerals Markhinite can be confused with other colorless sulfates found in the same environment, such as anglesite or langbeinite. Without specialized laboratory tests, distinguishing these minerals is impossible. ## Crystal Forms The mineral forms short, prismatic crystals that often combine into radial or irregular aggregates. It also occurs as thin crusts covering other minerals or rock.
Geological environment
## Genesis Markhinite is a mineral of volcanic origin, formed by sublimation from hot volcanic gases. It crystallizes directly from the gas phase in high-temperature fumaroles, at a temperature of approximately 400–450°C. ## Mineral Associations This mineral occurs in association with other rare fumarolic minerals, such as yavapaiite, alarsite, nabokoite, atlasovite, as well as more common ones like langbeinite, anglesite, and cotunnite. ## Localities The only confirmed locality of markhinite in the world is the Arsenatnaya fumarole, located in the second cinder cone of the Northern Breakthrough of the Great Fissure Eruption of Tolbachik volcano in Kamchatka, Russia.
Rarity
Extremely rare
Collector aspects
## Quality Criteria The quality of markhinite collector specimens, being a micromineral, is primarily assessed based on the richness and abundance of crusts on the rock matrix. The denser and more extensive the crystalline aggregates, the more valuable the specimen. The aesthetics of the entire specimen, including the presence of well-formed crystals of associated minerals, is also important. ## Popular Localities The only source of markhinite specimens is its type locality – Tolbachik volcano in Kamchatka. All specimens available on the collector's market (or rather, in exchange among specialists) originate from this single location.
Care and storage
## Cleaning Markhinite specimens are extremely delicate and small. Avoid wet cleaning and the use of any chemical agents. The only permissible method for dust removal is to use a soft, dry brush or a gentle stream of air from a photographic blower. ## What to Avoid **WARNING: The mineral contains thallium (Tl), which is a highly toxic element.** Absolutely avoid inhaling dust and direct skin contact. All manipulations with the specimen should be performed with gloves. The mineral may be sensitive to moisture and temperature changes. Protect it from water, chemicals, and high temperatures. ## Storage It is recommended to store specimens in tightly sealed, clearly labeled containers (e.g., "micromount box" type) to prevent accidental contact and dust dispersion. The container should be labeled with a toxicity warning. Keep away from children and pets.