Takanawaite-(Y)

Chemical formula: YTa<sup>₅+</sup>O<sub>₄</sub>

Takanawaite-(Y) is a very rare oxide mineral, a natural yttrium tantalate, found in granitic pegmatites.

## Characteristics Takanawaite-(Y) is an extremely rare oxide mineral, chemically classified as yttrium tantalate. It occurs as very small, tabular or prismatic crystals, reaching sizes up to 0.3 mm. It typically forms aggregates with other rare earth minerals. Its crystals are black, opaque, with a luster described as submetallic to resinous. ## Physical Properties This mineral is characterized by a Mohs hardness of approximately 6.5, making it relatively resistant to scratching. It has a high density of 7.35 g/cm³, which is typical for tantalum-bearing minerals. The luster is submetallic to resinous, and the streak is gray. It is brittle and exhibits an uneven fracture. ## Colors and Varieties It is observed exclusively in black. Due to its extreme rarity, no varieties have been distinguished. ## History and Name The mineral's name comes from its discovery locality in Takanawa, Nagano Prefecture, Japan. It was first described in 1972 by Japanese mineralogists Kin-ichi Sakurai, Kozo Nagashima, and Akira Kato. The suffix "-(Y)" in the name indicates the dominance of yttrium in its chemical composition, in accordance with the naming rules for rare earth minerals. ## Uses Due to its extreme rarity and microscopic crystal sizes, takanawaite-(Y) has no industrial applications. It is solely an object of scientific and collecting interest for specialized micromineral collectors.

Properties

Mohs hardness: 6.5
Luster: Sub-Metallic to Resinous
Streak: Gray
Density: 7.35
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of takanawaite-(Y) is possible almost exclusively using advanced laboratory methods, such as chemical composition analysis (EDS) and X-ray diffraction (XRD). Visually, it is a black, submetallic mineral occurring as very small, tabular crystals in association with other rare earth minerals in pegmatites. ## Distinguishing from Similar Minerals It can be confused with other black, heavy pegmatitic minerals, such as fergusonite, samarskite, euxenite, or columbite. Differentiation without specialized analysis is practically impossible. The key is the identification of tantalum and yttrium dominance in the chemical composition. ## Crystal Forms It forms very small, short prismatic or tabular crystals, often with irregular or poorly developed faces. It usually occurs as single, isolated crystals embedded in the host rock.

Geological environment

## Genesis It is a magmatic mineral, crystallizing in the late stages of the evolution of granitic pegmatites, rich in rare earth elements (REE), tantalum, and niobium. ## Mineral Associations It most commonly co-occurs with quartz, microcline, albite, biotite, as well as other rare earth minerals such as fergusonite-(Y), xenotime-(Y), allanite-(Ce), and zircon. ## Localities This is an extremely rare mineral, known from only a few localities worldwide. The most important ones include: - Type locality: Suishoyama pegmatite in Takanawa, Nagano Prefecture, Japan. - Other confirmed occurrences include pegmatites in the Evje og Hornnes area in Norway and in Szklarska Poręba-Huta in the Polish Karkonosze Mountains.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a takanawaite-(Y) specimen is primarily assessed based on the confirmation of its presence on the rock matrix. The most desirable specimens are those with the largest possible (though still microscopic), well-formed crystals. Contrast with a light host rock (e.g., quartz or feldspar) enhances visual appeal. Precise analytical documentation confirming the mineral's identity is crucial. ## Popular Localities The most "classic" specimens, though extremely rare, come from the type locality in Japan. Specimens from Norway and Poland are also highly valued by specialized micromineral collectors.

Care and storage

## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to the microscopic size of the crystals, mechanical cleaning (brushes) or chemical cleaning is highly risky and can lead to the destruction or loss of the mineral. Avoid contact with water. ## What to Avoid Avoid all chemicals, acids, and solvents. The mineral is brittle, so protect it from impacts, vibrations, and sudden temperature changes. Do not heat it or subject it to ultrasonic cleaning. ## Storage Takanawaite-(Y) specimens are typically micromounts. They should be stored in dedicated, sealed perky boxes, protected from dust, moisture, and mechanical damage. Store in stable temperature conditions, away from direct sunlight.

Sources

IMA Mineral List (CNMNC)