Hizenite-(Y)

Chemical formula: Ca<sub>2</sub>Y<sub>6</sub>(CO<sub>3</sub>)<sub>11</sub>·14H<sub>2</sub>O

Hizenite-(Y) is an extremely rare, hydrated calcium yttrium carbonate, forming spherical aggregates of tiny, platy crystals.

## Characteristics Hizenite-(Y) is a mineral belonging to the carbonate group. It occurs as spherical or hemispherical aggregates, reaching up to 2 mm in diameter. These aggregates are composed of very fine, platy or acicular crystals no longer than 100 micrometers. Individual crystals are colorless and transparent, but in aggregates, the mineral is white and translucent to opaque. ## Physical Properties The mineral is very soft, with a Mohs hardness of approximately 2. The luster of individual crystals is vitreous, while aggregates exhibit a pearly or dull luster. Due to the small size of the crystals and aggregates, precise determination of density is difficult; the calculated density is 2.76 g/cm³. ## Colors and Varieties The only known color of hizenite-(Y) is white. No varieties have been distinguished. ## History and Name The mineral's name comes from the former Japanese province of Hizen, where its discovery site (type locality) is located. The "-(Y)" suffix refers to the dominant rare earth element in its composition – yttrium. The mineral was approved by the International Mineralogical Association (IMA) in 2004, and its description was published in 2006. It was discovered by Japanese mineralogists, including Koichi Nagashima. ## Applications Due to its extreme rarity and microscopic size, hizenite-(Y) has no practical applications. It is solely an object of scientific interest and a collector's item for specialized micromineral collectors.

Properties

Mohs hardness
2
Luster
Pearly
Streak
White
Density
2.76
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Translucent to opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of hizenite-(Y) is almost exclusively possible using advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). Visually, it is characterized by its occurrence as white, spherical aggregates on basaltic rock. It reacts vigorously with hydrochloric acid. ## Distinguishing from Similar Minerals It can be confused with other secondary carbonates forming white, spherical aggregates, such as aragonite or calcite, as well as some zeolites (e.g., thomsonite). Differentiation requires specialized studies. Hizenite-(Y) is significantly softer than most zeolites and calcite. ## Crystal Forms It forms very fine, platy crystals, elongated along the [100] axis and flattened parallel to the {001} plane. These crystals combine into radial, spherical, or hemispherical aggregates.

Geological environment

## Genesis This mineral forms as a result of low-temperature hydrothermal processes. In the type locality, it fills gas vesicles and fractures in Miocene alkaline basalt. ## Mineral Associations It most commonly co-occurs with calcite, saponite (a smectite group mineral), and takanawaite-(Y). ## Localities The only confirmed locality of hizenite-(Y) in the world is the Mitsukoshi basalt quarry, located on the Higashi-Matsuura Peninsula in Karatsu City, Saga Prefecture (Kyushu Island), Japan.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of hizenite-(Y) specimens is assessed based on the size and development of spherical aggregates and their abundance on the host rock. The most prized specimens are those with clearly formed, undamaged spheres, contrasting with the dark background of the basaltic rock. Due to the microscopic nature of the mineral, the aesthetics of the entire rock fragment are crucial. ## Popular Localities The only source of specimens is the type locality – the Mitsukoshi quarry in Japan. Material from this location is extremely difficult to obtain.

Care and storage

## Cleaning Hizenite-(Y) specimens are extremely delicate and usually occur as microscopic coatings on the host rock. They should not be cleaned mechanically or chemically. If necessary, dust can be very carefully removed using a photographic air blower (non-contact). ## What to Avoid The mineral is sensitive to acids, which cause its rapid dissolution with the release of carbon dioxide. Contact with water, all chemicals, and ultrasound should be avoided. As a hydrated mineral, it may be sensitive to elevated temperatures, which can lead to its dehydration and destruction. ## Storage Specimens should be stored exclusively in specialized "micromount" boxes, protecting them from dust, mechanical damage, and sudden changes in humidity. Exposure to direct sunlight and vibrations should be avoided.

Sources

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