Whiteite-(CaMnMg)

Chemical formula: CaMn<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

Whiteite-(CaMnMg) is a rare, hydrated phosphate from the jahnsite group, forming small, tabular crystals in granitic pegmatites.

## Characteristics Whiteite-(CaMnMg) is a complex, hydrated phosphate belonging to the jahnsite group. It forms small but well-formed crystals, most often tabular or isometric in habit. Crystals rarely occur individually, usually forming fan-shaped, radial, or nearly parallel aggregates and clusters. Due to the small size of the crystals, typically ranging from fractions of a millimeter to several millimeters, it is a mineral valued mainly in the form of micromounts. ## Physical Properties This mineral is characterized by a hardness of 4 on the Mohs scale, making it relatively soft and susceptible to scratching. It has a vitreous luster and is transparent to translucent. Its density is approximately 2.55 g/cm³. ## Colors and Varieties Whiteite-(CaMnMg) occurs in a limited range of colors. Most often it is colorless, white, pale yellow, or light brown. The name "Whiteite" refers to the entire subgroup of minerals, and the suffix -(CaMnMg) precisely defines this specific mineral, in which calcium, manganese, and magnesium dominate in the appropriate positions in the crystal structure. ## History and Name The whiteite group of minerals was named after John Sampson White (born 1932), an American mineralogist and curator at the Smithsonian Institution. The species Whiteite-(CaMnMg) was first scientifically described in 1978 by Paul B. Moore and Jun Ito. The name reflects the chemical composition, indicating the dominance of calcium (Ca), manganese (Mn), and magnesium (Mg). ## Applications Due to its rarity and small crystal size, Whiteite-(CaMnMg) has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of rare minerals and micromounts.

Properties

Mohs hardness
4
Luster
Vitreous
Streak
White
Density
2.55
Cleavage
Good on {001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of Whiteite-(CaMnMg) is based on its characteristic appearance – small, tabular crystals with a vitreous luster, forming fan-shaped aggregates. The environment of occurrence (granitic pegmatites) and the presence of associated minerals, mainly other phosphates, are also crucial. ## Differentiation from Similar Minerals Distinguishing Whiteite-(CaMnMg) from other members of the jahnsite and whiteite groups (e.g., Whiteite-(CaFeMg) or Jahnsite-(CaMnMg)) is impossible without advanced chemical analyses (e.g., EDS). Visually, it can be confused with other secondary phosphates, such as roscherite or eosphorite. However, it differs from them in crystal form and physical properties, such as cleavage. ## Crystal Forms Crystals are monoclinic, tabular in habit, flattened parallel to the {001} plane. They often occur in radial or fan-shaped aggregates, as well as in sub-parallel intergrowths.

Geological environment

## Genesis Whiteite-(CaMnMg) is a secondary phosphate mineral that forms in the late stages of crystallization in complex, phosphorus-rich granitic pegmatites. It results from hydrothermal alteration or weathering of primary phosphates, such as triphylite. ## Mineral Associations This mineral often co-occurs with other secondary phosphates. Typical associated minerals include: rockbridgeite, collinsite, eosphorite, wardite, goyazite, as well as other members of the jahnsite and roscherite groups. ## Localities The most important and well-documented occurrences of this mineral worldwide are in several key localities. The type locality is the Hesnard pegmatite in Custer County, South Dakota, USA. Excellent specimens also come from the Rapid Creek and Big Fish River areas in the Yukon Territory, Canada, known for the occurrence of many rare phosphate minerals. This mineral has also been reported in Brazil (Minas Gerais) and Germany.

Rarity

Very rare

For collectors

## Quality Criteria The quality of Whiteite-(CaMnMg) specimens is primarily assessed based on the quality of micromounts. The most prized specimens are those with sharp, well-formed, and transparent crystals, forming aesthetic, fan-shaped aggregates. The contrast with the rock matrix and the presence of well-crystallized associated minerals, which increase the scientific and visual value of the specimen, are also important. Crystal size, even if exceeding 1-2 mm, is considered exceptional. ## Popular Localities The most sought-after specimens by collectors come from two regions: the Rapid Creek area in Yukon (Canada), from which numerous, well-formed aggregates originate, and from the pegmatites of South Dakota (USA), including the type locality.

Care and storage

## Cleaning Specimens should only be dry-cleaned, using a soft brush to remove dust. Due to the presence of water in the structure and possible reactivity, contact with water, and especially with chemicals, should be avoided. Ultrasonic cleaners are not permissible. ## What to Avoid The mineral is susceptible to mechanical damage due to its low hardness and good cleavage. It should be protected from scratching, impacts, and falls. High temperatures can lead to dehydration and destruction of crystals. Contact with acids and other chemical agents should be avoided. ## Storage It is recommended to store specimens in separate, padded micromount boxes to prevent contact with other minerals. They should be protected from dust, moisture, and direct sunlight, stored under stable room conditions.

Sources

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