Mangangordonite
Chemical formula: Mn<sup>2+</sup>Al<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>·8H<sub>2</sub>O
Mangangordonite is a very rare, hydrated manganese and aluminum phosphate, forming small, tabular crystals with a vitreous luster.
Description
## Characteristics Mangangordonite is a mineral from the phosphate group, chemically classified as a hydrated manganese and aluminum phosphate. It is the manganese analog of gordonite. It forms very small, tabular or prismatic crystals, rarely exceeding a few millimeters. It occurs as single, well-formed crystals, as well as in radial or fan-shaped aggregates. It is a brittle mineral. ## Physical Properties Its Mohs hardness is 3, making it a soft mineral, susceptible to scratching. It has a density of 2.36 g/cm³, relatively low for minerals. It is characterized by a vitreous luster and is transparent to translucent. It has good cleavage in one direction. ## Colors and Varieties It is most often colorless or white. It can also take on pale pink, yellowish, or greenish hues, depending on impurities. No named varieties are distinguished. ## History and Name The mineral's name refers to its chemical composition – the dominance of manganese (Mn) – and its structural similarity to gordonite. It was first described in 1976 by Peter B. Leavens, Cornelius S. Hurlbut Jr., and Joseph A. Nelen. The type locality is the Foote Lithium Co. mine in Kings Mountain, Cleveland County (North Carolina, USA). ## Applications Due to its rarity and small crystal size, mangangordonite has no industrial application. It is exclusively a valued and sought-after collector's mineral.
Diagnostic features
## Identification Mangangordonite can be recognized by its characteristic, small, tabular crystals, often forming radial aggregates. Low hardness, vitreous luster, and occurrence in paragenesis with other rare phosphates in granitic pegmatites are key diagnostic features. A chemical reaction confirming the presence of manganese is the ultimate proof. ## Distinguishing from Similar Minerals It can be confused with other secondary phosphates of similar appearance. The most difficult to distinguish is gordonite, which is its magnesium analog and often has an identical appearance – differentiation requires chemical analysis. It can also be confused with paravauxite or metavauxite, from which it differs in crystal form and optical properties. ## Crystal Forms Crystals are typically tabular, flattened parallel to the {010} cleavage plane, or short prismatic. They often occur as rosetted, fan-shaped, or radial aggregates of small crystals growing on the surface of other minerals.
Geological environment
## Genesis It is a secondary mineral, formed in complex granitic pegmatites. It forms as a result of hydrothermal alteration of primary phosphate minerals, such as triphylite-lithiophilite, in the late stages of pegmatite crystallization. ## Mineral Associations Mangangordonite co-occurs with a wide range of other, often rare, phosphate minerals. At the type locality (Foote Mine), it was found in association with gordonite, montgomeryite, paravauxite, kingsmountite, rockbridgeite, strengite, and laueite. ## Localities The most important and classic locality for mangangordonite is the Foote Lithium Co. mine in North Carolina, USA, from which the best known specimens originate. It has also been reported from the Tip Top mine in Custer County (South Dakota, USA). Outside the United States, its occurrences are few and less well documented.
Rarity
Very Rare
Collector aspects
## Quality Criteria The most highly prized mangangordonite specimens are those with sharp, well-formed, and transparent crystals. Due to their typically small size, crystal size is a key factor influencing value. Aesthetic, radial aggregates and placement on a contrasting rock matrix also enhance attractiveness. Specimens with a visible pinkish or greenish color are more sought after than colorless ones. ## Popular Localities Specimens from the type locality – the Foote mine in North Carolina – are by far the most desired by collectors. They are considered the global standard for this mineral. Specimens from the Tip Top mine in South Dakota are also highly regarded.
Care and storage
## Cleaning Mangangordonite specimens should be cleaned with the utmost care. Due to its low hardness (3 on the Mohs scale), it is susceptible to scratching. For dust removal, it is best to use a soft brush. If necessary, it can be rinsed in distilled water, then gently dried with compressed air or left to air dry. Ultrasonic cleaners should be avoided. ## What to Avoid Mangangordonite is sensitive to acids and other strong chemicals. As a hydrated mineral, it can be damaged (dehydrated) by high temperatures, so heating should be avoided. Prolonged exposure to direct sunlight is also not recommended. ## Storage It is recommended to store specimens in separate, padded boxes to avoid contact with harder minerals that could scratch it. It is best to keep it in stable conditions, away from heat sources and dust.