Parabrandtite

Chemical formula: Ca<sub>2</sub>Mn<sup>2+</sup>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>·2H<sub>2</sub>O

Parabrandtite is a rare, hydrated calcium manganese arsenate, forming tiny, acicular crystals of white or pinkish color.

## Characteristics Parabrandtite is a mineral from the arsenate group, belonging to the roselite series. It occurs as very small, acicular or bladed crystals, rarely exceeding 1 mm in length. These crystals often form radial aggregates, rosettes, or spherical clusters. Due to the small size of the crystals, its macroscopic features are difficult to observe without magnification. ## Physical Properties Parabrandtite crystals are characterized by a vitreous luster and are transparent to translucent. The Mohs hardness is approximately 3.5, and its density is about 3.65 g/cm³. The mineral exhibits perfect cleavage in one direction. ## Colors and Varieties Parabrandtite is usually colorless or white. It can take on delicate shades of pink or brown, likely due to impurities or manganese oxidation. No named varieties are distinguished. ## History and Name The mineral was first described in 1957 by Paul B. Moore. Its name refers to its structural and chemical similarity to brandtite, with the prefix "para-" which in crystallography indicates a polymorphic or closely related form. It was discovered in the Sterling Hill Mine in Ogdensburg, New Jersey (USA). ## Uses Parabrandtite has no industrial application. It is solely an object of interest for collectors specializing in rare minerals or minerals from specific localities (so-called "systematists").

Properties

Mohs hardness
3.5
Luster
Vitreous
Streak
White
Density
3.65
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Triclinic

Diagnostic features

## Identification Amateur identification of parabrandtite is practically impossible. It requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS). Preliminary identification is based on crystal form (tiny needles, radial aggregates), co-occurrence with other manganese minerals and arsenates, and locality. ## Distinguishing from Similar Minerals Parabrandtite is visually indistinguishable from brandtite, with which it is dimorphous (having the same chemical composition but a different crystal structure). It can also be confused with other white or pink arsenates, such as roselite, talmessite, or picropharmacolite. Definitive differentiation is only possible through laboratory analysis. ## Crystal Forms It forms elongated, acicular or bladed crystals with a rhombic cross-section, terminating in a point. These crystals most often occur as radial or stellate aggregates, as well as spherulitic (spherical) clusters.

Geological environment

## Genesis Parabrandtite is a secondary mineral, forming in the oxidation zones of ore deposits, particularly in metamorphic zinc, manganese, and iron deposits. It forms as a result of the alteration of primary minerals containing arsenic and manganese. ## Mineral Associations It most commonly co-occurs with other arsenates and manganese minerals. In its type locality (Sterling Hill, USA), it was found in association with sarkinite, allactite, brandtite, baryte, and franklinite. In other localities, it may occur with roselite, talmessite, erythrite, or pharmacosiderite. ## Localities The most important and classic occurrences of this mineral are the Sterling Hill Mine in Ogdensburg, New Jersey, USA (type locality) and the Gozaisho Mine in Fukushima Prefecture, Japan. It is also known from several other places in the world, including the Wenzel Mine in the Black Forest (Germany) and the Aghbar deposit in Morocco.

Rarity

Very rare

For collectors

## Quality Criteria For collectors, the richness and aesthetics of crystal aggregates are most important. Specimens with well-formed, radial groups of crystals, clearly contrasting with the matrix rock, are highly valued. Color contrast, for example, pink needles on a dark matrix, significantly increases the visual and collector's value of the specimen. Due to the microscopic nature of the mineral, specimens suitable for viewing under magnification (so-called micromounts) are standard. ## Popular Localities The most sought-after specimens by collectors come from the type locality - Sterling Hill in the USA. Well-formed crystals from the Gozaisho Mine in Japan and from Aghbar in Morocco, where attractive pink aggregates originate, are also highly prized.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its fragility and potential reactivity, washing in water, especially using ultrasonics, should be avoided. ## What to Avoid Avoid contact with acids and other chemicals that may damage the mineral. Parabrandtite is brittle, so it should be protected from impacts and vibrations. It should not be heated. ## Storage It is recommended to store specimens in stable conditions, in closed display boxes, to protect them from dust and mechanical damage. It is best to keep it away from moisture.

Sources

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