Miyawakiite-(Y)

Chemical formula: &#₉₇₄₄;Y₄Fe₂+₂(Si₈O₂₀)(CO₃)₄(H₂O)₃

A rare yttrium and iron silicate, distinguished by a unique combination of silicates and carbonates in its structure and its occurrence as radial aggregates.

## Characteristics Miyawakiite-(Y) is a complex yttrium and iron silicate, belonging to the group of rare minerals. It forms characteristic, radial or spherulitic aggregates that can reach up to 1 mm in diameter. Individual crystals within these aggregates are in the form of lamellae or fibers. It is a translucent mineral with a vitreous luster. ## Physical Properties This mineral is characterized by a hardness of approximately 4 on the Mohs scale. Its density is significantly higher than average, at about 3.85 g/cm³. It does not exhibit cleavage, and its fracture is uneven. Some sources indicate that it may show weak fluorescence under ultraviolet light. ## Colors and Varieties The typical color of miyawakiite-(Y) is pale yellow to yellowish-brown. No color varieties or commercial varieties have been described. ## History and Name The mineral was approved by the IMA in 2007. Its name honors Ritsuro Miyawaki (born 1959), a Japanese mineralogist from the National Museum of Nature and Science in Tokyo, for his contributions to rare-earth mineral research. The suffix "-(Y)" refers to the dominant rare-earth element in its composition – yttrium. ## Applications Due to its extreme rarity, miyawakiite-(Y) has no industrial applications. It is solely an object of scientific interest and a collector's item for specialized rare mineral collectors.

Properties

Mohs hardness: 4
Luster: Vitreous
Streak: White
Density: 3.85
Cleavage: None
Fracture: Uneven
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Key diagnostic features include its occurrence as small, radial or spherulitic aggregates with a yellowish color. High density is also a characteristic feature. However, final identification requires advanced analytical methods, such as X-ray spectroscopy (XRD and EDS), due to its similarity to other rare carbonate-silicate minerals. ## Distinguishing from similar minerals It can be confused with other rare-earth minerals forming similar aggregates, such as some minerals from the gatelite group or kainosite-(Y). Visual differentiation is practically impossible and requires specialized studies to confirm chemical composition and crystal structure. ## Crystal forms Crystals are in the form of elongated lamellae or fibers, which combine into radial, spherical aggregates (spherulites). Single, well-formed crystals are not observed.

Geological environment

## Genesis It is a hydrothermal mineral. It forms in the late stages of crystallization in granitic pegmatites, filling small fissures and cavities. In its type locality (Suishoyama mine), it occurs in druses within biotite granite. ## Mineral associations This mineral co-occurs with minerals such as quartz, microcline, biotite, tengerite-(Y), lokkaite-(Y), as well as rare-earth carbonates and silicates. ## Localities The only confirmed and described occurrence of this mineral in the world is its type locality: Suishoyama mine, Iizaka district, Fukushima Prefecture, Japan.

Rarity

Extremely rare

For collectors

## Quality criteria The quality of a specimen primarily depends on the size and degree of development of the spherulitic aggregates. Specimens where the aggregates are clearly visible, undamaged, and contrast with the surrounding rock (matrix) are most valued. Due to their microscopic nature, any specimen with aggregates visible to the naked eye is considered exceptional. ## Popular localities The only source of specimens is the Suishoyama mine in Japan. Material from this locality is extremely rare and very difficult to acquire on the collector's market.

Care and storage

## Cleaning Utmost caution is recommended. The safest method is to use compressed air to remove dust. Any wet cleaning is discouraged due to potential reactivity and the delicacy of the aggregates. ## What to avoid Contact with acids and other chemicals that could damage the mineral must be strictly avoided. Avoid ultrasonic cleaning and mechanical cleaning (e.g., with brushes), which could destroy the delicate, fibrous aggregates. Protect from high temperatures and humidity. ## Storage Specimens should be stored under stable conditions, in a closed display box, to protect them from dust, mechanical damage, and sudden changes in humidity. Due to the small size of the specimens, a box with magnification (a "micromount" type) is ideal.

Sources

IMA Mineral List (CNMNC)