Magnesiohatertite

Chemical formula: NaNaCa(MgFe₃+)(As₅+O₄)₃

Magnesiohathorite is an extremely rare arsenate of the alluaudite group, discovered in Poland, forming microscopic, yellowish-green, radial aggregates.

## Characteristics Magnesiohathorite is a mineral from the arsenate class, belonging to the alluaudite supergroup. It occurs as very small, spherulitic or radial aggregates, whose diameter rarely exceeds 1 mm. These aggregates are composed of microscopic, elongated, prismatic or acicular crystals. Due to their small size, individual crystals are difficult to observe with the naked eye and require magnification. ## Physical properties The mineral is characterized by a hardness of approximately 3.5 on the Mohs scale, which makes it relatively soft and susceptible to scratching. The luster is described as vitreous, sometimes greasy on aggregate surfaces. It is translucent. The calculated density is approximately 4.29 g/cm³, which is a high value, typical for arsenates containing heavy elements. ## Colors and varieties The typical color of magnesiohathorite is yellowish-green to olive-green. The intensity of the color may vary within a single aggregate. No color or commercial varieties of this mineral have been distinguished. ## History and name The mineral was officially recognized by the International Mineralogical Association (IMA) in 2015. Its name refers to its chemical composition – the dominant role of magnesium (magnesio) and its structural similarity to hathorite. It was discovered in the dump of the former "Jaskółka" adit in Radzimowice in the Kaczawskie Mountains (Lower Silesia, Poland), which is its type locality. ## Applications Due to its extreme rarity and microscopic size, magnesiohathorite has no industrial applications. It is solely an object of scientific interest and a valuable and sought-after acquisition for specialized collectors of rare minerals and micromounts.

Properties

Mohs hardness: 3.5
Luster: Vitreous
Streak: Pale greenish yellow
Density: 4.29
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of magnesiohathorite in field or amateur conditions is practically impossible. Its characteristic features are small, spherulitic aggregates of a yellowish-green color, occurring in a specific environment. Certain identification requires advanced analytical techniques, such as electron microscopy with chemical composition analysis (EDS/WDS) and X-ray diffraction (XRD). ## Distinguishing from similar minerals This mineral can be confused with other secondary arsenates of a greenish color, such as scorodite, pharmacosiderite, beudantite, or mimetite. Differentiation is based on chemical analysis and crystal structure examination. The characteristic form of radial aggregates and mineral paragenesis can be a helpful clue. ## Crystal forms It forms spherulitic (spherical) and radial aggregates composed of small, elongated crystals with a prismatic to acicular habit.

Geological environment

## Genesis Magnesiohathorite is a secondary mineral, formed in the oxidation zone (weathering) of polymetallic ore deposits. It forms as a result of the alteration of primary arsenic-bearing minerals, mainly arsenopyrite, under low temperature and pressure conditions. ## Mineral associations In its type locality (Radzimowice, Poland), it co-occurs with other rare secondary minerals, such as arseniosiderite, beudantite, pharmacosiderite, scorodite, and with common goethite. ## Localities The most important and historically first occurrence of magnesiohathorite in the world is the post-mining dumps in the area of the former mine in Radzimowice in the Kaczawskie Mountains in Poland. It has also been reported in the Oumlil mine in Morocco.

Rarity

Extremely rare

For collectors

## Quality criteria The most highly valued specimens are those that have well-formed, distinct spherulitic aggregates of intense, yellowish-green color, deposited on a contrasting matrix. The size of the aggregates, their quantity on the specimen, and the richness of associated minerals (especially other rare arsenates) significantly increase their collector's value. ## Popular localities The only locality from which specimens of collector's significance originate is its place of discovery – Radzimowice in Poland. Specimens from this locality are particularly sought after by collectors of type minerals (discovered in a given country) and micromount specialists.

Care and storage

## Cleaning Magnesiohathorite specimens are extremely delicate and most often microscopic in size. Cleaning, if absolutely necessary, should be limited to very careful dust removal with a soft, dry brush. Water, chemicals, and ultrasonic cleaners should be avoided, as they can irreversibly damage the specimen. ## What to avoid As an arsenate, the mineral is potentially toxic – hands should be washed after contact with the specimen. It should be protected from any impacts and abrasions due to its low hardness. Moisture, sudden temperature changes, and exposure to chemicals should be avoided. ## Storage It is recommended to store specimens in specialized, sealed "micromount" boxes, which protect against dust, moisture, and mechanical damage. Each specimen should be properly labeled, taking into account its fragility and potential toxicity.

Sources

IMA Mineral List (CNMNC)