Matioliite

Chemical formula: NaMgAl₅(PO₄)₄(OH)₆·2H₂O

Matioliite is a very rare, hydrated sodium, magnesium, and aluminum phosphate, forming small, hexagonal crystals with a white color and pearly luster.

## Characteristics Matioliite is a mineral from the phosphate group, chemically classified as a hydrated sodium, magnesium, and aluminum phosphate. It occurs as very small, tabular crystals with a hexagonal outline, not exceeding 0.2 mm. These crystals form rosette-like or spherulitic aggregates. Due to the small size of the crystals, its macroscopic features are difficult to observe without magnification. ## Physical Properties The mineral has a hardness of approximately 3.5 on the Mohs scale. It exhibits a pearly luster on cleavage surfaces and a vitreous luster on other faces. It is transparent to translucent. The calculated density is 2.81 g/cm³. ## Colors and Varieties Matioliite is colorless to white. No colored or commercial varieties have been identified. ## History and Name The mineral is named in honor of Hermes F. Matioli (born 1957), a Brazilian mineral collector who found the first samples. Matioliite was approved as a new mineral by the International Mineralogical Association (IMA) in 2008. It was described by Daniel Atencio, José M. V. Coutinho, André C. Doriguetto, Marcelo B. Andrade, and Luiz A. D. Menezes Filho, who provided the material for study. ## Uses Due to its extreme rarity and microscopic size, matioliite has no industrial applications. It is solely an object of scientific and collecting interest for specialized collectors of rare minerals (known as micromounts).

Properties

Mohs hardness
5
Color
Blue to colourless
Luster
Pearly
Streak
White
Density
0
Cleavage
Perfect on {0001}
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of matioliite is almost exclusively possible using advanced analytical methods, such as X-ray diffraction (XRD) and chemical spectroscopy (EDS/WDS). Visually, under high magnification, characteristic small, hexagonal crystals forming rosette-like aggregates on the host rock can be observed. ## Distinguishing from Similar Minerals Matioliite can be confused with other secondary, white phosphates occurring in similar environments, such as wardite, crandallite, or variscite. Differentiation without specialized equipment is practically impossible. Chemical and crystallographic analysis is key. ## Crystal Forms The mineral forms thin, tabular crystals with a hexagonal outline. These crystals often combine into rosettes, spherulites, or irregular aggregates on the rock surface.

Geological environment

## Genesis Matioliite is a secondary mineral, forming in hydrothermal zones within granitic pegmatites. It forms in vugs and fractures, likely as a result of the alteration of earlier phosphate minerals in the presence of solutions rich in sodium, magnesium, and aluminum. ## Mineral Associations At its type locality (Sapucaia mine), matioliite coexists with minerals such as frondelite, wardite, eosphorite, zircon, quartz, albite, and muscovite. ## Localities The only confirmed locality of matioliite in the world is its type locality – the Sapucaia mine, near the town of Sapucaia do Norte, in Minas Gerais state, Brazil.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of matioliite specimens is assessed based on the richness and aesthetics of the microscopic aggregates. Most valued are samples with well-formed, sharp crystals forming distinct rosettes. Contrast with the matrix and the presence of associated minerals are also important. Due to its microscopic nature, the purity and size of individual crystals are less significant than the overall presentation of the aggregate within the microscope's field of view. ## Popular Localities The only source of matioliite specimens is the Sapucaia mine in Brazil. All samples available on the collector's market originate from this single locality.

Care and storage

## Cleaning Specimens of matioliite, which are typically micromounts, should not be cleaned mechanically or chemically. The safest method is to gently remove dust using a photographic air blower or compressed air from a safe distance. ## What to Avoid Avoid contact with all chemicals, including acids and bases. The mineral is sensitive to ultrasound and sudden temperature changes. It should not be soaked in water, especially hot water. ## Storage Specimens should be stored in specialized micromount boxes that protect them from dust, humidity, and mechanical damage. Store in stable room conditions, away from direct sunlight and heat sources.

External references

Sources

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