Gunmaite
Chemical formula: (Na<sub>2</sub>Sr)Sr<sub>2</sub>Al<sub>10</sub>(PO<sub>4</sub>)<sub>4</sub>F<sub>14</sub>(OH)<sub>12</sub>
Gunmaite is an extremely rare phosphate mineral, discovered in Japan, forming colorless, prismatic crystals in radial aggregates.
Description
## Characteristics Gunmaite is a complex sodium, strontium, and aluminum phosphate, visually appearing as colorless to white, elongated, prismatic crystals. It most commonly forms small, radial or fan-shaped aggregates, with individual crystals rarely exceeding 1 mm in length. Due to its microscopic size, it is primarily available as a micromount specimen. ## Physical Properties The mineral is characterized by a vitreous luster and is transparent to translucent. Its density, calculated based on chemical composition and crystal structure, is 3.43 g/cm³. Its Mohs hardness has not yet been determined. ## Colors and Varieties Gunmaite occurs exclusively in colorless or white forms. No colored varieties or trade names are known. ## History and Name The mineral's name comes from its discovery locality – Gunma Prefecture in Japan. It was officially approved by the International Mineralogical Association (IMA) in 2022 under number IMA2022-030, making it one of the newly described minerals. ## Applications Gunmaite has no industrial applications. Its significance is purely scientific and collectible, being an object of interest for specialists and collectors of rare minerals.
Diagnostic features
## Identification Amateur identification of gunmaite is practically impossible. Definitive identification requires advanced analytical methods such as X-ray diffraction (XRD) and chemical microanalysis (EDS). A preliminary indication may be its specific form – radial aggregates of colorless, acicular crystals – and its co-occurrence with other rare phosphates within a pyrophyllite deposit. ## Distinguishing from Similar Minerals Gunmaite can be visually confused with many other colorless minerals forming acicular or prismatic crystals, such as augelite, wardite, or some zeolites. However, its unique geological environment (pyrophyllite deposit) and paragenesis with specific minerals, e.g., trolleite, lazulite, or scorzalite, are key for differentiation. Final distinction is only possible through laboratory analysis. ## Crystal Forms Gunmaite crystals are prismatic, elongated along one axis. They almost always occur in radial, stellate, or fan-shaped aggregates.
Geological environment
## Genesis Gunmaite forms as a result of hydrothermal processes within pyrophyllite deposits. It is a secondary mineral, crystallizing in rock fractures and cavities. ## Mineral Associations This mineral occurs in association with a rich assemblage of other minerals, mainly phosphates. It most commonly co-occurs with pyrophyllite, diaspore, fluorapatite, trolleite, scorzalite, lazulite, augelite, goyazite, svanbergite, woodhouseite, hinsdalite, florencite-(Ce), xenotime-(Y), and monazite-(Ce). ## Localities The only confirmed locality for gunmaite in the world is its type locality – the Hinomaru-Nako mine in Kanra District, Gunma Prefecture, Japan.
Rarity
Extremely rare
Collector aspects
## Quality Criteria For gunmaite collectors, the most important criteria for evaluating a specimen are: the sharpness and habit of the crystals, the size and aesthetics of the radial aggregates, and the richness and visual appeal of associated minerals on the rock matrix. Due to the microscopic nature of the mineral, specimens are evaluated under magnification. ## Popular Localities The most prized, and indeed the only available specimens, come from the Hinomaru-Nako mine in Japan. This is the sole source of this mineral on the global collector's market.
Care and storage
## Cleaning Gunmaite specimens, being microscopic and delicate, generally do not require cleaning and attempts to do so should be avoided. Any attempts at mechanical or chemical cleaning can irreversibly damage the fragile crystal structure. If necessary, a gentle stream of air from a photographic blower bulb can be used to remove loose dust particles. ## What to Avoid Avoid contact with all chemicals, acids, and detergents. The mineral is sensitive to shocks and impacts – it should be handled with utmost care. Cleaning in ultrasonic cleaners is absolutely forbidden. ## Storage Specimens should be stored exclusively in specialized, sealed "micromount" boxes that protect against dust, moisture, and mechanical damage. Each specimen should be properly labeled with its name and locality.