Maghrebite

Chemical formula: MgAl<sub>2</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>·8H<sub>2</sub>O

Maghrebsite is a hydrated magnesium aluminum arsenate, forming characteristic, spherical aggregates with a silky luster and blue-green color.

## Characteristics Maghrebsite is a hydrated magnesium aluminum arsenate. It occurs as small, spherical or hemispherical aggregates, rarely exceeding 1 mm in diameter. These aggregates have a radial structure, composed of very fine, acicular or lamellar crystals. The surface of the aggregates is often uneven, and the individual crystals give them a characteristic, silky luster. ## Physical properties This mineral is relatively soft, with a Mohs hardness of approximately 2. It is light, with a density close to 2.63 g/cm³. The crystals are flexible and can be bent. The luster is distinctly silky on the surface of the aggregates, and vitreous on individual crystals. ## Colors and varieties Maghrebsite is characterized by an attractive, blue-green color. No varieties have been distinguished. ## History and name The mineral's name comes from the Maghreb region in Northwest Africa, where it was discovered. It was first described in 2007 by Werner Krause, H.-J. Bernhardt, H. Effenberger, and M. L. Garcí-Guinea based on specimens found in the Bou Azzer mine in Morocco. ## Uses Due to its rarity and small specimen size, maghrebsite is of scientific and collector's interest only.

Properties

Mohs hardness
2
Luster
Silky, Vitreous
Streak
Pale greenish blue
Density
2.63
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Characteristic features of maghrebsite include its unique mode of occurrence as small, spherical aggregates with a radial structure, blue-green color, and silky luster. The size of the aggregates, not exceeding 1 mm, is also an important clue. ## Distinguishing from similar minerals Maghrebsite can be confused with other secondary arsenic minerals of similar color, such as agardite or some varieties of conichalcite. However, it is distinguished by its specific, spherical aggregate form and silky luster. Accurate identification requires advanced analytical methods (XRD, EDS). ## Crystal forms It forms spherical or hemispherical aggregates with an internal radial structure. These aggregates are composed of very fine, elongated crystals with an acicular or lamellar habit.

Geological environment

## Genesis Maghrebsite is a secondary mineral, formed in the oxidation zones (gossans) of cobalt-nickel-arsenic ore deposits. It forms as a result of the weathering of primary arsenides, such as skutterudite, in the presence of magnesium and aluminum minerals. ## Mineral associations It most commonly co-occurs with quartz, dolomite, erythrite, roselite, wendwilsonite, talmessite, and skutterudite. It occurs on the surface of these minerals or in small rock fractures. ## Localities The only confirmed locality of maghrebsite in the world is its type locality - the Bou Azzer mining district, near the town of Tazenakht in Ouarzazate Province, Morocco.

Rarity

Very rare

For collectors

## Quality criteria The most prized specimens are those that possess numerous, well-formed, and undamaged spherical aggregates of intense, blue-green color. Contrast with the rock matrix (e.g., white dolomite or quartz) and the presence of associated minerals, such as pink erythrite, are also important. ## Popular localities All known collector specimens come from a single location in the world - the Bou Azzer mine region in Morocco, which makes them particularly desirable for collectors specializing in rare minerals or minerals from this locality.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using only compressed air to remove dust. Contact with water is inadvisable due to the risk of damaging delicate aggregates and potential solubility. ## What to avoid Absolutely avoid contact with water, acids, and other chemicals. The mineral is very soft and brittle, sensitive to any impacts and abrasions. It should not be heated or exposed to prolonged strong light. ## Storage It is recommended to store specimens in closed, stable containers (such as "micromount boxes") to protect them from dust, moisture, and mechanical damage. Avoid storage in humid environments.

Sources

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