Mieite-(Y)

Chemical formula: Y₄Ti₄+(SiO₄)₂O[F,(OH)]₆

Mieite-(Y) is a very rare silicate mineral that forms microscopic, transparent crystals with a vitreous luster.

## Characteristics Mieite-(Y) is a silicate mineral characterized by a complex chemical composition containing yttrium, titanium, silicon, oxygen, fluorine, and hydrogen. It occurs as very small, tabular or bladed crystals, rarely exceeding 0.2 mm in length. They are colorless and transparent, which, combined with their small size, makes their observation require specialized optical equipment. ## Physical Properties Mieite-(Y) crystals exhibit a vitreous luster. Due to the microscopic size of the crystals, precise determination of many physical properties, such as hardness or density, is difficult. The density has been calculated based on the chemical formula and unit cell parameters, with a value of approximately 4.61 g/cm³. ## History and Name The mineral's name, "mieite," comes from Mie Prefecture in Japan, where its type locality, the Komuro quarry, is located. It was officially approved by the International Mineralogical Association (IMA) in 2013. The suffix "-(Y)" indicates the dominance of yttrium in its chemical composition, in accordance with the naming rules for rare earth minerals.

Properties

Luster: Vitreous
Streak: White
Density: 4.61
Cleavage: None
Fracture: Uneven
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of mieite-(Y) is possible only through advanced laboratory methods, such as X-ray diffraction (XRD) and chemical analysis using an electron microprobe (EDS/WDS). Visual identification in the field or even under a standard microscope is impossible due to its appearance and co-occurrence with other similar minerals. ## Distinguishing from Similar Minerals It can be confused with many other colorless, microscopic silicates found in the same environment, such as quartz, fluorite, or other rare earth minerals. Certain differentiation requires specialized analysis of chemical composition and crystal structure. ## Crystal Forms It forms very small, elongated, bladed or tabular crystals, usually grouped into small aggregates. Single, well-formed crystals are extremely rare.

Geological environment

## Genesis Mieite-(Y) forms under hydrothermal conditions within granitic pegmatites. Its occurrence is associated with late stages of crystallization, where rare earth elements, titanium, and fluorine become concentrated. ## Mineral Associations At the type locality, it co-occurs with minerals such as quartz, microcline, albite, fluorite, xenotime-(Y), zircon, fergusonite-(Y), and monazite-(Ce). ## Localities The only confirmed locality of mieite-(Y) in the world is the Komuro quarry, located near Miyano, in Mie Prefecture, Japan.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, mieite-(Y) is of interest exclusively to specialized "micromount" collectors. The value of a specimen is primarily determined by the abundance and quality of crystals visible under a microscope, and confirmation of their identity through analysis. The aesthetics of the host rock and the presence of associated minerals are also important. ## Popular Localities The only source of specimens is the type locality – the Komuro quarry in Japan. Material from this location is extremely difficult to obtain.

Care and storage

## Cleaning Due to its extreme rarity and microscopic size, mieite-(Y) specimens are practically not subject to cleaning under amateur conditions. Any manipulation should be carried out exclusively in laboratory conditions using specialized equipment. Specimens are found on the host rock and should not be removed from it. ## What to Avoid Avoid contact with any chemicals, ultrasound, and sudden temperature changes. The crystals are brittle and susceptible to mechanical damage. Specimens should not be exposed to abrasion or scratching. ## Storage Specimens should be stored in stable conditions, in specialized "micromount" boxes that protect them from dust, moisture, and physical damage. It is best to keep them away from direct sunlight and heat sources.

Sources

IMA Mineral List (CNMNC)