Glass-(Y)
Chemical formula: NaCa₂Y₂(Be₄Si₈O₂₄)F₄
An extremely rare mineral from the gadolinite group, forming colorless, vitreous crystals in syenite pegmatites.
Description
## Characteristics Glass-(Y) is a very rare beryllium, sodium, calcium, and yttrium silicate, belonging to the gadolinite supergroup. It occurs as small aggregates (up to 0.5 mm) composed of thin, bladed crystals, which reach up to 0.2 mm in length. It is colorless and transparent, with a characteristic vitreous luster, from which its name is derived. ## Physical Properties The mineral is characterized by a vitreous luster and is transparent. Its calculated density is approximately 3.48 g/cm³. The Mohs hardness has not yet been determined. ## Colors and Varieties Glass-(Y) is a colorless mineral. No colored varieties or trade names are known. ## History and Name The mineral was officially approved by the International Mineralogical Association (IMA) in 2019. Its name refers to its glassy appearance and the dominance of yttrium (Y) in its chemical composition. It is the yttrium analog of glass-(Ce). It was discovered in Tvedalen, Norway, which is its type locality. ## Applications Due to its extreme rarity and microscopic crystal sizes, Glass-(Y) has no practical applications. It is solely an object of scientific and collecting interest among micromineral collectors.
Diagnostic features
## Identification Accurate identification is only possible using advanced analytical methods, such as Raman spectroscopy or X-ray microanalysis (EDS/WDS), due to its microscopic size and lack of unique macroscopic features. It occurs as colorless, vitreous blades in rock cavities. ## Distinguishing from Similar Minerals It can be confused with other colorless microminerals found in the same environment, such as chiavennite-(Y), elpidite, or even quartz. Definitive distinction requires chemical analysis to confirm the composition, especially the presence of beryllium and the dominance of yttrium over other rare earth elements. ## Crystal Forms It forms thin, bladed, elongated crystals, often gathered into small, radial or disordered aggregates.
Geological environment
## Genesis Glass-(Y) forms in the late stage of crystallization of syenite pegmatites, crystallizing within small cavities and fissures (miarolitic cavities). ## Mineral Associations It co-occurs with minerals such as aegirine, albite, chiavennite-(Y), elpidite, fergusonite-(Y), genthelvite, wulfenite, and zircon. ## Localities The only confirmed occurrence worldwide (type locality) is the syenite quarry in Tvedalen, in the Larvik region, Vestfold county, Norway.
Rarity
Extremely rare
Collector aspects
## Quality Criteria For microminerals such as Glass-(Y), the value of a specimen is primarily determined by the abundance and quality of crystals on the rock matrix. Specimens with well-formed, transparent crystals forming distinct, aesthetic aggregates, preferably accompanied by other rare associated minerals, are highly valued. ## Market Prices There is a lack of reliable market price data due to the extreme rarity and non-commercial nature of the mineral. Specimens primarily go to research institutions and highly specialized micromineral collections, often on an exchange basis. ## Popular Localities The only source of specimens is the type locality in Tvedalen, Norway.
Care and storage
## Cleaning Due to their microscopic size and delicacy, specimens containing glass-(Y) should not be cleaned mechanically or chemically. If necessary, compressed air (from a safe distance and at low pressure) can be used to remove loose dust particles. ## What to Avoid Contact with all chemicals, ultrasonic cleaners, and sudden temperature changes should be strictly avoided. The crystals are brittle and can be very easily damaged or detached from the matrix. ## Storage Specimens should be stored in specialized, sealed micromount boxes, which protect them from dust, shocks, and mechanical damage.