Magnesioqingheiite

Chemical formula: Na<sub>2</sub>Mg(MgAl)(PO<sub>4</sub>)<sub>3</sub>

Magnesioqingheiite is a very rare sodium, magnesium, and aluminum phosphate, forming tiny, colorless crystals in pegmatites.

## Characteristics Magnesioqingheiite is a member of the alluaudite group, distinguished from other minerals in this group by the dominance of magnesium in specific positions of the crystal structure. It occurs as very small, tabular or lath-like crystals, usually not exceeding 0.2 mm in length. The crystals are colorless and transparent, with a vitreous luster. Due to its size, it is a mineral that can be identified almost exclusively using advanced analytical techniques. ## Physical Properties Magnesioqingheiite crystals exhibit a hardness of approximately 5 on the Mohs scale. They are brittle, and their density, calculated from crystallographic data, is about 3.25 g/cm³. The mineral does not show fluorescence under ultraviolet light. ## Colors and Varieties Magnesioqingheiite is colorless. No colored varieties or trade names are known. ## History and Name The mineral was first described in 2018 by a team of mineralogists led by Anthony R. Kampf. The name "magnesioqingheiite" refers to its chemical composition (dominant magnesium) and its structural relationship to the mineral qingheiite. It was approved by the International Mineralogical Association (IMA) under number 2018-080. The holotype comes from the Foote Lithium Co. mine in North Carolina, USA.

Properties

Mohs hardness
5
Luster
Vitreous
Streak
White
Density
3.25
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of magnesioqingheiite in the field or based on visual characteristics is impossible. Recognition requires specialized laboratory equipment, such as an electron microscope with EDS analysis (energy-dispersive spectroscopy) to determine chemical composition, and X-ray diffraction to confirm the crystal structure. ## Distinguishing from Similar Minerals It can be confused with other minerals from the alluaudite group, such as qingheiite, alluaudite, or ferroalluaudite, as well as with other small, colorless phosphates found in pegmatites. Definitive differentiation is possible only based on precise chemical analysis showing the dominance of magnesium in two key structural positions (M1 and M2). ## Crystal Forms It forms very small, elongated crystals with a lath-like or tabular appearance, reaching up to 0.2 mm in length. They occur as single, isolated crystals on the surface of other minerals.

Geological environment

## Genesis Magnesioqingheiite is a secondary mineral, formed in the late stage of crystallization of granitic pegmatites. It forms as a result of hydrothermal or metasomatic processes that lead to changes in the composition of previously crystallized primary phosphate minerals, such as triphylite. ## Mineral Associations At the type locality (Foote mine), it co-occurs with albite, quartz, microcline, as well as other rarer phosphates, such as whitmoreite and triplite. ## Localities The only confirmed occurrence of magnesioqingheiite worldwide is its type locality: Foote Lithium Co. mine, Kings Mountain district, Cleveland County, North Carolina, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, magnesioqingheiite is not evaluated according to typical collector criteria, such as size or color. The value of a specimen lies in its scientific significance and analytically confirmed identity. The most valuable are holotype and cotype specimens, on which the mineral was first studied. For collectors specializing in systematics or "micro" minerals, any specimen with well-formed, even the smallest, crystals embedded in a contrasting rock matrix will be valuable.

Care and storage

## Cleaning Due to the extreme rarity and microscopic size of the crystals, magnesioqingheiite specimens should not be cleaned in any way. Any attempt at mechanical or chemical cleaning risks irreversible destruction of the mineral. These specimens are of scientific value only and should be preserved in an untouched state. ## What to Avoid Avoid any contact with chemicals, water, ultrasound, and sudden temperature changes. The crystals are brittle and susceptible to mechanical damage. ## Storage Specimens should be stored exclusively in specialized micromount containers, protecting them from dust, shocks, and moisture. Store in stable room conditions, away from sources of vibration.

Sources

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