Ehrleite

Chemical formula: Ca<sub>2</sub>Zn<sup>2+</sup>Be(PO<sub>4</sub>)<sub>2</sub>(PO<sub>3</sub>OH)·4H<sub>2</sub>O

Ehrleite is a very rare, hydrated beryllium, zinc, and calcium phosphate, forming colorless, bladed crystals.

## Characteristics Ehrleite is an extremely rare mineral from the phosphate group, chemically classified as a hydrated beryllium, zinc, and calcium phosphate. It occurs as very small, bladed or tabular crystals, usually not exceeding 1 mm in length. The crystals are colorless and transparent, often forming radial aggregates or small, rosette-like clusters on the surface of the host rock. Due to its chemical composition, which includes toxic beryllium, it requires careful handling. ## Physical Properties The mineral is characterized by a hardness of approximately 4 on the Mohs scale. It has a vitreous luster and is transparent. The calculated density is 2.64 g/cm³. The crystals exhibit perfect cleavage in one direction. ## History and Name Ehrleite was discovered at the Tip Top Mine in Custer County, South Dakota (USA). It was described and approved as a new mineral species by the International Mineralogical Association (IMA) in 1983. The mineral is named in honor of Howard Ehrle, an American mineral collector who first found and drew attention to this mineral.

Properties

Mohs hardness
4
Luster
Vitreous
Streak
White
Density
2.64
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Transparent
Crystal system
Triclinic

Diagnostic features

## Identification Amateur identification of ehrleite is practically impossible. It requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS) to confirm its unique composition with calcium, zinc, and beryllium. Visually, small, colorless, bladed crystals in radial aggregates on pegmatite may be an indication. ## Distinguishing from Similar Minerals It can be confused with other rare, secondary phosphates found in pegmatites, such as herderite, wardite, or childrenite. Differentiation without specialized equipment is impossible; key factors include co-occurrence with other minerals from the Tip Top Mine and its unique chemical composition. ## Crystal Forms It forms elongated, bladed or thin-tabular crystals, which often arrange into radial or rosette-like aggregates. The crystals are small, usually less than 1 millimeter in length.

Geological environment

## Genesis Ehrleite is a secondary mineral that forms in complex granitic pegmatites. It crystallizes during the late, hydrothermal stage of pegmatite evolution, as a result of the alteration of previously formed phosphate and beryllium minerals in the presence of zinc-rich solutions. ## Mineral Associations This mineral occurs in association with other rare phosphates, especially at its type locality (Tip Top Mine). It co-occurs with minerals such as roscherite, tiptopite, montgomeryite, englishite, smoky quartz, and microcline. ## Localities The only confirmed occurrence of ehrleite in the world is its type locality – the Tip Top Mine, located near Custer, in Custer County, South Dakota, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of an ehrleite specimen is determined by the richness and development of crystals within the aggregate. The most desirable specimens are those with clearly visible, radial clusters of colorless, vitreous crystals, well-contrasted against a darker host rock. Due to the microscopic size of the crystals, specimens are evaluated under magnification. Every authentic specimen is considered extremely valuable. ## Popular Localities The only source of ehrleite specimens is the Tip Top Mine in South Dakota, USA. Material from this locality is extremely rare and sought after by specialized systematic mineral and "micromount" collectors.

Care and storage

## Cleaning Due to its extreme rarity and delicacy, mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used to remove dust. Avoid contact with water and chemicals. ## What to Avoid The mineral contains beryllium, which is a toxic element. Avoid inhaling dust and direct skin contact. It should not be heated or exposed to acids. Specimens are brittle and susceptible to mechanical damage. ## Storage Ehrleite specimens should be stored exclusively in specialized, sealed "micromount" containers to protect them from damage and dust, and to prevent accidental contact with toxic dust. Store in stable conditions, away from vibrations and sources of moisture.

Sources

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