Proshchenkoite-(Y)
Chemical formula: (Y,REE,Ca,Na,Mn<sup>2+</sup>)<sub>15</sub>Fe<sup>2+</sup>Ca(P,Si)Si<sub>6</sub>B<sub>3</sub>(O,F)<sub>48</sub>
A very rare yttrium and rare-earth element silicate from the vicanite group, with a complex chemical composition.
Description
## Characteristics Proshchenkoite-(Y) is a mineral with a very complex composition, belonging to the vicanite group. It forms granular aggregates or imperfectly developed, short, prismatic crystals, usually of small size. Its color ranges from yellowish-brown to reddish-brown. It is a brittle mineral with a vitreous luster. ## Physical Properties The mineral is translucent. Its Mohs hardness is 5.5, and its density is 4.16 g/cm³. It does not exhibit cleavage, and its fracture is uneven. The streak is light brown. ## Colors and Varieties Observed colors are shades of brown: yellowish-brown and reddish-brown. No color or commercial varieties have been distinguished. ## History and Name The mineral was officially recognized by the IMA in 2016. Its name honors Evgeny Grigorievich Proshchenko (1928–1995), a Russian geologist who studied the pegmatites where this mineral was first found. The suffix "-(Y)" indicates the dominance of yttrium in the chemical composition at a specific site in the crystal structure. ## Applications Due to its extreme rarity, proshchenkoite-(Y) has no commercial or industrial applications. It is of purely scientific significance and is an object of interest for specialized collectors of microscopic minerals.
Diagnostic features
## Identification Identification of proshchenkoite-(Y) is impossible without advanced analytical techniques. This requires chemical composition analysis (EDS/WDS) and X-ray diffraction (XRD). A key clue is its occurrence in a specific geological environment at its only known locality. ## Differentiation from Similar Minerals It can be confused with other minerals from the vicanite group (e.g., okanoganite-(Y)) and with associated rare-earth minerals such as britholite-(Y). Definitive differentiation is only possible based on detailed laboratory studies. ## Crystal Forms It most commonly occurs as granular or massive aggregates. Less frequently, it forms imperfectly developed, short crystals with a hexagonal cross-section.
Geological environment
## Genesis Proshchenkoite-(Y) is a mineral of magmatic origin, crystallizing in the late stage of evolution of granitic pegmatites, rich in alkaline and rare-earth elements. ## Mineral Associations This mineral co-occurs with minerals such as miaskite, albite, quartz, aegirine, zircon, minerals from the pyrochlore group, britholite-(Y), danalite, and fluorite. ## Localities The only confirmed occurrence in the world is the Pilipenko pegmatite vein in the Zolotaya Gora massif, in the Southern Urals, Chelyabinsk Oblast, Russia. This is its type locality.
Rarity
Extremely rare
Collector aspects
## Quality Criteria As a microscopic mineral, the most valuable specimens are those with visible, even if imperfect, crystalline forms. The presence on matrix in association with other rare accessory minerals is also highly valued. A key factor in value is confirmation of identification by a reputable laboratory. ## Popular Localities The only source of specimens is the type locality in the Southern Urals, Russia. Material from this location is extremely difficult to acquire.
Care and storage
## Cleaning Extreme caution is recommended. Specimens should only be cleaned mechanically, using a soft brush to remove dust. Due to its rarity, contact with water and chemicals should be avoided unless absolutely necessary. Ultrasonic cleaning is prohibited. ## What to Avoid Avoid contact with acids and other chemicals that may react with the complex composition of the mineral. Abrupt temperature changes are also inadvisable. ## Storage Specimens, usually microscopic, should be stored under stable conditions, in a specialized "micromount" box, protected from dust and mechanical damage. Direct exposure to sunlight should be avoided.