Ermeloite

Chemical formula: Al(PO<sub>4</sub>)·H<sub>2</sub>O

Ermeloite is a newly discovered aluminum phosphate, forming colorless, prismatic crystals with a vitreous luster, found in Spain.

## Characteristics Ermeloite is a hydrated aluminum phosphate, approved as a new mineral species by the International Mineralogical Association (IMA) in 2023. It occurs as very small, elongated, prismatic crystals, typically not exceeding 150 micrometers in length and 30 micrometers in width. The crystals are colorless and transparent, often forming radial or randomly oriented aggregates on the surface of the host rock. Due to their small size, visual features are only discernible under high magnification. ## Physical Properties Ermeloite crystals are characterized by a vitreous luster. The Mohs hardness has been estimated at approximately 3, which is similar to calcite. The mineral is brittle. The density calculated from crystallographic data is 2.68 g/cm³. ## Colors and Varieties To date, only colorless ermeloite crystals have been observed. No colored or commercial varieties have been distinguished. ## History and Name The mineral's name comes from its discovery locality – the municipality of Ermelo in the province of Pontevedra, Galicia (Spain). It was described by a group of Spanish scientists, and its discovery was officially approved in 2023 (IMA2023-0 Ermeloite). It is the natural analogue of the synthetic compound Al(PO₄)·H₂O, previously known from laboratory research. ## Uses Ermeloite, as a newly discovered and extremely rare mineral, has no industrial applications. Its significance is purely scientific and collectible, being an object of interest for specialized research institutions and micromineral collectors.

Properties

Mohs hardness
~3
Luster
Vitreous
Streak
White
Density
2.68
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Transparent
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of ermeloite is impossible without advanced analytical techniques. It requires the use of a scanning electron microscope (SEM) with EDS analysis to determine the chemical composition and X-ray diffraction (XRD) to confirm the crystal structure. Visually, under high magnification, characteristic, fine, prismatic crystals in radial aggregates can be observed. ## Distinguishing from Similar Minerals Ermeloite is dimorphous with berlinite (AlPO₄), which crystallizes in the trigonal system and has a different structure. It may be confused with other secondary phosphate minerals of similar appearance, such as variscite or strengite, but it differs from them in crystal habit and chemical composition. Definitive differentiation requires specialized studies. ## Crystal Forms Ermeloite forms elongated, prismatic crystals with a nearly rectangular cross-section. These crystals group into small, radial or disordered aggregates on the rock surface.

Geological environment

## Genesis Ermeloite is a hydrothermal mineral. It forms in the late stages of granite pegmatite crystallization, as a result of hydrothermal solutions interacting with earlier phosphate minerals, such as triplite. It occurs in vugs and fractures within altered triplite. ## Mineral Associations This mineral co-occurs with quartz, albite, muscovite, triplite, zwieselite, barbosalite, strengite, cyrilovite, rockbridgeite, phosphosiderite, and leucophosphite. ## Localities The only confirmed locality for ermeloite worldwide is its type locality: a granite pegmatite near O Pando mountain, in the municipality of Ermelo, Pontevedra province, Galicia, Spain.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, the collector's value of ermeloite primarily depends on the quality of the specimen at the micro scale. The most desirable specimens are those with well-formed, sharp, and undamaged crystals, forming rich, aesthetic aggregates on a small fragment of the host rock. The transparency and luster of the crystals, visible under a microscope, also enhance the specimen's attractiveness. Due to its extreme rarity, any analytically confirmed specimen is valuable. ## Popular Localities The only source of ermeloite specimens is its type locality in Ermelo, Spain. Material from this location is extremely limited and primarily available through research institutions and specialized micromineral collectors.

Care and storage

## Cleaning Ermeloite specimens are extremely small and delicate. Any mechanical cleaning should be avoided. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. Contact with water or other liquids is not recommended due to the unknown reaction of the mineral. ## What to Avoid Avoid contact with chemicals, acids, and bases. Due to its low hardness (approx. 3), the mineral is very susceptible to scratches and mechanical damage. It should be protected from vibrations, impacts, and sudden temperature changes. ## Storage Ermeloite specimens should be stored exclusively in specialized micromount boxes, which protect them from dust, moisture, and physical damage. Exposure should be away from direct sunlight and heat sources.

Sources

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