Whiteite-(CaFeMg)

Chemical formula: CaFe<sup>2+</sup>Mg<sub>2</sub>Al<sub>2</sub>(PO<sub>4</sub>)<sub>4</sub>(OH)<sub>2</sub>·8H<sub>2</sub>O

A rare phosphate mineral from the whiteite group, found as small, tabular crystals with a vitreous luster.

## Characteristics Whiteite-(CaFeMg) is a hydrated phosphate belonging to the whiteite group. It forms very small, usually not exceeding 1 mm, tabular or bladed crystals. They most often occur as rosette-like or radial aggregates, as well as single crystals grown on other minerals. Due to its small size, its visual characteristics are difficult to observe without magnification. ## Physical Properties The mineral is characterized by a vitreous luster and is transparent to translucent. Its Mohs hardness is approximately 3.5, classifying it as a relatively soft mineral. The density calculated based on the chemical formula and unit cell parameters is 2.75 g/cm³. ## Colors and Varieties Whiteite-(CaFeMg) occurs in shades from colorless to pale yellow or yellowish-brown. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral is named in honor of John Sampson White (born 1933), an American mineralogist and curator of collections at the Smithsonian Institution. It was first described in 1978 by P.B. Moore and T. Araki. The "(CaFeMg)" suffix in the name specifies the chemical composition of this particular end-member in the whiteite group, indicating the dominance of calcium, iron, and magnesium at specific positions in the crystal structure.

Properties

Mohs hardness
3.5
Luster
Vitreous
Streak
White
Density
2.75
Cleavage
Good on {001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Amateur identification of whiteite-(CaFeMg) is practically impossible due to its rarity and small crystal size. Recognition requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS), which allow confirmation of its structure and composition. ## Distinguishing from Similar Minerals It can be confused with other minerals from the whiteite group (e.g., whiteite-(MnFeMg) or whiteite-(CaMnMg)) and other microcrystalline phosphates occurring in similar parageneses, such as wardite or strengite. Definitive differentiation is possible only based on chemical analysis. ## Crystal Forms Crystals are most often tabular, flattened parallel to the {001} plane, and tend to form radial or rosette-like aggregates. They also occur as single, overgrown crystals.

Geological environment

## Genesis Whiteite-(CaFeMg) is a secondary mineral, forming in complex granitic pegmatites rich in phosphates. It originates from hydrothermal processes or the weathering of primary phosphate minerals, such as triplite. ## Mineral Associations This mineral coexists with other phosphates, such as strengite, phosphosiderite, rockbridgeite, hureaulite, stewartite, as well as quartz, muscovite, and albite. ## Localities The most important and well-documented occurrences of this mineral worldwide include the Tip Top Mine near Custer, South Dakota (USA), which is its type locality. It is found there in pegmatites. Other confirmed occurrences include pegmatites in Hagendorf-Süd, Bavaria (Germany).

Rarity

Very rare

For collectors

## Quality Criteria The collector's appeal of a specimen primarily depends on the abundance and development of its crystals. Samples with distinct, well-formed, rosette-like crystal aggregates contrasting with the rock matrix are most valued. Due to the small size of the crystals, specimens suitable for photomicrography (so-called micromounts) are particularly sought after. Color, although usually pale, may slightly influence value if it is more saturated. ## Popular Localities By far the most valued and classic specimens come from the type locality – the Tip Top Mine in South Dakota, USA.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using a soft brush to remove dust. Due to its softness and potential reactivity, contact with water, especially detergents, should be avoided. ## What to Avoid Avoid ultrasonic cleaners, chemicals, acids, and sudden temperature changes. The mineral is soft and easily scratched. As a hydrated mineral, it may be sensitive to desiccation in low humidity conditions. ## Storage It is recommended to store specimens in stable conditions, in closed display boxes, to protect delicate crystals from mechanical damage and dust. Avoid exposure to direct sunlight and high temperatures.

Sources

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