Amaterasuite

Chemical formula: Sr<sub>4</sub>Ti<sup>4+</sup><sub>6</sub>Si<sub>4</sub>O<sub>23</sub>(OH)Cl

Extremely rare, black strontium and titanium silicate, forming prismatic crystals with a submetallic luster, discovered in Japan.

## Characteristics Amaterasuit is a very complex titanium and strontium silicate, belonging to the sorosilicate group. It forms small, prismatic or acicular crystals, which usually do not exceed 1 mm in length. They most often occur in radial or fan-shaped aggregates. The mineral has a characteristic black color and submetallic luster, giving it an appearance resembling some metal oxides. ## Physical properties The Mohs hardness of amaterasuit is approximately 6. It is an opaque mineral with a measured density of 4.02 g/cm³. It exhibits good cleavage in one plane. Its luster is described as submetallic, and the streak it leaves on a porcelain plate is grayish-white. ## Colors and varieties This mineral occurs exclusively in black. No color varieties or commercial varieties are known. ## History and name The mineral's name comes from Amaterasu-ōmikami, the Japanese sun goddess, referencing the country of its discovery. It was officially approved by the International Mineralogical Association (IMA) in 2019. It was discovered in the Ise Kōzan quarry, Wakayama Prefecture, Japan. ## Applications Due to its extreme rarity and occurrence as microscopic crystals, amaterasuit has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized micromineral collectors.

Properties

Mohs hardness
6
Luster
Sub-metallic
Streak
Greyish-white
Density
4.02
Cleavage
Good on {100}
Fracture
Uneven
Transparency
Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of amaterasuit under amateur conditions is practically impossible. Key features include black color, submetallic luster, radial aggregates of small, prismatic crystals, and a specific occurrence environment. Definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Distinguishing from similar minerals Amaterasuit can be confused with other black, acicular minerals occurring in similar parageneses, such as aegirine or arfvedsonite. Differentiation is based on subtle differences in crystal shape, luster, and physical properties, but this is not feasible without specialized equipment. Its unique chemical composition is the ultimate diagnostic criterion. ## Crystal forms Crystals are prismatic to acicular, often elongated. They typically form radial aggregates spreading from a common center, as well as fibrous or fan-shaped clusters.

Geological environment

## Genesis Amaterasuit is a high-temperature mineral. It forms under specific conditions, in sanidinite xenoliths (rock fragments entrained by magma) within volcanic rocks, such as quartz latite. Its formation is associated with metasomatism and crystallization from rare-element-rich magmatic fluids. ## Mineral associations This mineral co-occurs with other rare minerals typical of its formation environment. In the type locality, it was found in association with arfvedsonite, aegirine, sanidine, quartz, titanite, allanite-(Ce), and zircon. ## Locations The only confirmed locality of amaterasuit in the world is its type locality – the Ise Kōzan quarry, located in Nakatsu, Hidakagawa, Wakayama Prefecture on Honshu Island, Japan.

Rarity

Extremely rare

For collectors

## Quality criteria The quality of an amaterasuit specimen is primarily assessed based on the richness and aesthetics of the aggregates. The most desirable samples are those with well-formed, radial clusters with good luster, contrastingly set on a lighter rock matrix. The sharpness and undamaged state of individual crystals within the aggregate are also important, which can only be assessed under a microscope. ## Popular localities The only source of specimens is the Ise Kōzan quarry in Japan. Material from this locality is extremely difficult to obtain and appears on the collector's market sporadically, mainly in closed circles among specialized micromineral collectors.

Care and storage

## Cleaning Specimens should only be dry-cleaned, using a soft brush to remove dust. Due to the small size of the crystals and potential fragility, avoid washing in water and any mechanical interference. Ultrasonic cleaning is absolutely not recommended. ## What to avoid Avoid contact with chemicals, especially acids. The mineral should be protected from sudden temperature changes and direct, prolonged sunlight, although there is no evidence of it fading. ## Storage It is recommended to store specimens in specialized "micromount" boxes, which protect them from dust, moisture, and mechanical damage. It is best to display them under a microscope.

Sources

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