Overite

Chemical formula: CaMgAl(PO₄)₂(OH)(H₂O)₄

Overite is a rare, hydrated calcium, magnesium, and aluminum phosphate, forming small, vitreous crystals with a characteristic light green color.

## Characteristics Overite is a hydrated phosphate belonging to the overite group. It occurs as small, tabular or prismatic crystals, often aggregated into radial clusters, rosettes, or spherical masses. The most commonly encountered specimens form thin, vitreous coatings and crusts on the surface of host rocks. It is a brittle mineral. ## Physical Properties Overite has a hardness ranging from 3.5-4 on the Mohs scale. Its density is approximately 2.53 g/cm³. It has a vitreous luster and is translucent. It exhibits perfect cleavage in one direction, which may be visible on some crystals. ## Colors and Varieties This mineral most commonly ranges in color from light green, apple-green, to colorless. In transmitted light, it is colorless. No named varieties are distinguished. ## History and Name Overite was first described in 1940. Its name honors James Over (1886-1961), an American mineral collector who discovered the mineral in 1938 in Clay Canyon, Utah, USA. This locality is considered its type locality. ## Uses Overite has no industrial application. It is solely a mineral of scientific and collector's interest.

Properties

Mohs hardness: 3.5-4
Luster: Vitreous
Streak: White
Density: 2.53
Cleavage: On {010}, perfect; on {100}, poor.
Fracture: Uneven
Transparency: Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Characteristic features of overite include its light green color, vitreous luster, and typical forms of occurrence as radial aggregates, rosettes, or thin coatings. It is relatively light and soft. It often occurs in paragenesis with other rare phosphates. ## Distinguishing from Similar Minerals Overite can be confused with other green phosphates, such as wavellite or wardite. It differs from wavellite in crystal form – wavellite forms perfectly spherical aggregates with a distinctly radial internal structure, while overite aggregates are often less regular. Wardite is usually harder (5 on the Mohs scale) and crystallizes in the tetragonal system, forming characteristic pseudo-octahedral crystals. ## Crystal Forms Overite crystals are small, tabular or short-prismatic. They most often form radial or fibrous aggregates, rosettes, as well as spherical masses and thin coatings on rocks.

Geological environment

## Genesis Overite is a secondary mineral, forming in the oxidation zones of phosphate deposits. It forms as a result of low-temperature hydrothermal processes or through the action of surface waters on primary phosphate minerals in pegmatites or sedimentary rocks. ## Mineral Associations This mineral often co-occurs with other phosphates, such as wardite, wavellite, montgomeryite, crandallite, englishite, as well as with quartz, apatite, and clay minerals. ## Localities The most important and classic locality for overite is Clay Canyon in Utah County, USA, from which the best specimens originate. It is also known from several other localities in the USA (South Dakota, Nevada). Outside the United States, its occurrences have been reported in Spain (Galicia) and Germany (Hagendorf-Süd mine in Bavaria).

Rarity

Rare

For collectors

## Quality Criteria Specimens with well-formed, sharp crystals forming aesthetic rosettes or radial aggregates are most valued by collectors. An intense, apple-green color significantly enhances the attractiveness of a specimen. Contrast with the rock matrix and absence of mechanical damage are also important. Specimens from the classic Clay Canyon locality are particularly sought after. ## Popular Localities Undoubtedly, the most desirable specimens come from the type locality - Clay Canyon in Utah, USA. Specimens from the Hagendorf-Süd mine in Germany are also valued in collections specializing in systematic minerals.

Care and storage

## Cleaning Overite specimens should be cleaned very carefully, using a soft brush to remove dust. Brief rinsing in distilled water is permissible, followed by thorough drying of the specimen. Ultrasonic cleaners should be avoided. ## What to Avoid The mineral is sensitive to acids and strong detergents, which can damage it. It should be protected from high temperatures, which can lead to dehydration and destruction of its structure. Avoid prolonged exposure to direct sunlight. ## Storage Overite is brittle and relatively soft, so it should be stored in a separate, padded box, away from harder minerals, to prevent scratches. It is best displayed in a closed cabinet, protecting it from dust and mechanical damage.