Pilawite-(Y)

Chemical formula: Ca₂Y₂Al₄(SiO₄)₄O₂(OH)₂

Pilawite-(Y) is a very rare sorosilicate mineral, discovered in Poland, forming yellowish-green, zoned crystals.

## Characteristics Pilawite-(Y) is a mineral belonging to the gadolinite group and the datolite supergroup. It occurs as small, well-formed, tabular or prismatic crystals, reaching up to 1 mm in size. These crystals often exhibit zoning, with visible differences in coloration between individual growth zones. They are typically transparent to translucent. ## Physical Properties The mineral is characterized by a hardness of approximately 6 on the Mohs scale. It has a vitreous luster and a white streak. The calculated density is about 4.13 g/cm³. It does not exhibit cleavage, and its fracture is uneven to conchoidal. ## Colors and Varieties Pilawite-(Y) most commonly has a yellowish-green or green color. Distinct color zoning is observed, where crystal cores may be darker and outer parts lighter. No varieties have been distinguished. ## History and Name The mineral's name comes from its discovery locality – a pegmatite in Piława Górna, Lower Silesia, Poland. It was officially approved by the International Mineralogical Association (IMA) in 2013 (number 2013-011). It was described by a team of mineralogists, including Adam Pieczka and Frank C. Hawthorne. ## Applications Due to its extreme rarity and small crystal size, pilawite-(Y) has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of rare minerals and microminerals.

Properties

Mohs hardness: 6
Luster: Vitreous
Streak: White
Density: 4.13
Cleavage: None
Fracture: Uneven to conchoidal
Transparency: Transparent to translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of pilawite-(Y) under amateur conditions is practically impossible. It requires advanced analytical methods, such as X-ray microanalysis (EDS/WDS) to determine its chemical composition (with yttrium dominance) and X-ray diffraction (XRD) to confirm its crystal structure. Visually, it can be suspected based on its characteristic locality, mineral paragenesis, and crystal form and color. ## Differentiation from Similar Minerals It can be confused with other minerals from the gadolinite group, such as gadolinite-(Y) or hingganite-(Y), as well as with other greenish silicates found in pegmatites, e.g., epidote or vesuvianite. Definitive differentiation is only possible based on chemical and structural analysis. ## Crystal Forms It forms small, tabular or short-prismatic crystals, often blocky in habit. The crystals are well-formed, with distinct faces. They occur as single, overgrown crystals or in small aggregates within the matrix rock.

Geological environment

## Genesis Pilawite-(Y) is a mineral of magmatic origin, crystallizing in the late stage of granite pegmatite evolution, in zones rich in rare earth elements, especially yttrium. It forms under hydrothermal conditions, in rock cavities and fissures. ## Mineral Associations This mineral co-occurs with other minerals typical of granite pegmatites, such as albite, microcline, quartz, biotite, as well as rarer minerals containing rare earth elements, e.g., xenotime-(Y), fergusonite-(Y), gadolinite-(Y), and hingganite-(Y). ## Localities The only confirmed locality of pilawite-(Y) in the world is its type locality – a pegmatite quarry in Piława Górna, in the Sowie Mountains Block in Lower Silesia, Poland.

Rarity

Extremely rare

For collectors

## Quality Criteria The most highly valued pilawite-(Y) specimens are those with well-formed, sharp, and undamaged crystals that are clearly visible against a contrasting rock matrix (most often albite or microcline). Intense green coloration and visible color zoning are desirable. Crystal size is a key factor – specimens with crystals exceeding 1 mm are exceptionally rare and valuable. ## Popular Localities The only source of specimens is the mine in Piława Górna, Poland. Material from this locality is extremely rare and sought after by collectors specializing in type minerals (discovered at a given location) and microminerals.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using compressed air to remove dust. Due to the small size of the crystals and their fragility, mechanical cleaning (brushes) and contact with water and chemical agents, which could damage the delicate crystals or matrix rock, are not recommended. ## What to Avoid Avoid ultrasonic cleaners, all chemicals, acids, and detergents. The mineral should be protected from sudden temperature changes and direct, prolonged exposure to sunlight, which could theoretically affect its color. ## Storage It is recommended to store specimens in stable conditions, in closed "micromount" boxes, which protect them from dust, mechanical damage, and humidity. Display should be away from sources of vibration and direct light.

Sources

IMA Mineral List (CNMNC)