Magnesiochlorophoenicite

Chemical formula: Mg<sub>3</sub>Zn<sup>2+</sup><sub>2</sub>As<sup>5+</sup>O<sub>4</sub>(OH,O)<sub>6</sub>

Magnesiochlorophoenicite is a rare magnesium and zinc arsenate, forming aggregates of small, acicular crystals with a characteristic red color.

## Characteristics Magnesiochlorophoenicite is a rare mineral from the arsenate group, chemically classified as a basic magnesium and zinc arsenate. It occurs as fibrous or radial aggregates, as well as clusters of small, acicular or bladed crystals. Its most characteristic visual feature is an intense red to reddish-purple color. ## Physical Properties This mineral has a hardness ranging from 3-4 on the Mohs scale. It exhibits a vitreous to pearly luster, especially visible on cleavage surfaces. It is a translucent mineral. Its density is approximately 3.7 g/cm³. ## Colors and Varieties The predominant and essentially only observed color of magnesiochlorophoenicite is red, transitioning into purplish-red hues. No distinct color varieties or commercial forms are recognized. ## History and Name The mineral's name refers to its chemical composition – the dominance of magnesium (magnesio) and its visual resemblance to chlorophoenicite. It was formally described as a new mineral in 1979 by Pete J. Dunn. The type locality, from which the first described specimens originated, is the Sterling Mine in Sterling Hill, Ogdensburg, New Jersey, USA. ## Applications Due to its rarity and small crystal size, magnesiochlorophoenicite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or minerals from Franklin and Sterling Hill.

Properties

Mohs hardness
3-4
Luster
Vitreous to pearly
Streak
Reddish
Density
3.7
Cleavage
Good on {001}
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Key features for identifying magnesiochlorophoenicite include its characteristic red to reddish-purple color, fibrous or radial habit of aggregates, and co-occurrence with other minerals from the Franklin deposit in New Jersey. Vitreous to pearly luster and relatively low hardness are also helpful indicators. ## Distinguishing from Similar Minerals This mineral can be confused with chlorophoenicite, to which its name alludes. Differentiation requires advanced analytical methods, such as chemical analysis (EDS/WDS), which will show the dominance of magnesium over manganese in magnesiochlorophoenicite. Visually, it may resemble other fibrous, red minerals, but its unique formation environment (mineral associations) is a strong diagnostic clue. ## Crystal Forms Magnesiochlorophoenicite crystals are typically very small, acicular or bladed, elongated along one axis. They most often form radial, stellate, or fibrous aggregates and crusts on other minerals, mainly on calcite.

Geological environment

## Genesis It is a secondary mineral, formed as a result of hydrothermal or metamorphic processes within metamorphosed zinc, iron, and manganese ore deposits. Its formation is associated with the mobilization and recrystallization of elements under specific chemical and physical conditions. ## Mineral Associations Magnesiochlorophoenicite most commonly occurs in association with calcite, franklinite, willemite, zincite, chlorophoenicite, and various rare arsenates and silicates characteristic of the Franklin-Sterling Hill deposit. ## Localities The only confirmed and well-documented occurrence of magnesiochlorophoenicite in the world is its type locality – the zinc ore deposit at Sterling Hill, Ogdensburg, Sussex County, New Jersey, USA. This is a classic locality for many rare minerals.

Rarity

Very rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with clearly formed, radial aggregates of intense red color, contrasting with a light background, most often white calcite. The size and richness of magnesiochlorophoenicite clusters on the rock matrix significantly increase the specimen's value. Purity and lack of damage to the delicate, acicular crystals are crucial. ## Popular Localities As this mineral is known from only one location in the world, all collectible specimens originate from the Sterling Mine in Sterling Hill, New Jersey, USA. This mine is now closed and converted into a museum, meaning new specimens are no longer being acquired, and material on the market comes exclusively from old collections.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its low hardness and potential reactivity, washing in water should be avoided, especially the use of any detergents. If it is necessary to remove loose contaminants, compressed air can be used from a safe distance. ## What to Avoid Contact with acids and other chemicals, which can damage or dissolve the mineral, must be absolutely avoided. Its low hardness makes it very susceptible to scratches and mechanical damage. It should not be heated or exposed to prolonged strong sunlight. ## Storage Collectible specimens of magnesiochlorophoenicite should be stored in separate, padded boxes or display cases to avoid contact with harder minerals. It is best to keep them in stable room conditions, away from moisture, dust, and direct light.

Sources

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