Pauloabibite

Chemical formula: NaNb<sup>₅+</sup>O<sub>₃</sub>

Pauloabibite is a rare sodium niobate, forming cubic crystals with a metallic luster, found in caverns within carbonatites.

## Characteristics Pauloabibite is a mineral from the oxide group, chemically classified as sodium niobate. It occurs in the form of well-developed, single cubic crystals, reaching up to 0.2 mm in size. These crystals are opaque, black in color, and exhibit a metallic luster. They typically grow on the walls of small voids (caverns) within carbonatite rocks. ## Physical Properties This mineral is characterized by a metallic luster and a black streak. Its Mohs hardness is 5.5, and its density, calculated based on the chemical formula and unit cell parameters, is 4.96 g/cm³. It shows no cleavage, and its fracture is conchoidal. ## Colors and Varieties Pauloabibite occurs exclusively in black. No color varieties or commercial varieties are known. ## History and Name The mineral's name honors Paulo Abib, a Brazilian mining engineer and distinguished mineral collector, in recognition of his contribution to the preservation of Brazil's mineralogical heritage. Pauloabibite was approved as a new mineral species by the International Mineralogical Association (IMA) in 2017 (IMA2017-052). It was discovered in the Seis Lagos carbonatite complex in Amazonas State, Brazil. ## Applications Due to its extreme rarity and microscopic crystal size, pauloabibite has no industrial applications. It is solely an object of scientific and collecting interest for specialized collectors of rare minerals.

Properties

Mohs hardness: 5.5
Luster: Metallic
Streak: Black
Density: 4.96
Cleavage: None
Fracture: Conchoidal
Transparency: Opaque
Crystal system: Cubic

Diagnostic features

## Identification Identification of pauloabibite is based on its characteristic crystal form – perfect cubes. Key features also include its black color, metallic luster, and specific occurrence environment (caverns in carbonatites). Due to its microscopic size, final confirmation requires advanced analytical methods such as Raman spectroscopy or chemical analysis (EDS). ## Distinguishing from Similar Minerals Pauloabibite can be confused with other black, metallic minerals found in similar environments, such as magnetite, pyrochlore, or lueshite. It differs from magnetite by its lack of magnetic properties and cubic crystal form (magnetite more often forms octahedra). From lueshite, which has the same chemical composition, it differs in its crystallographic system (lueshite is orthorhombic). From pyrochlore, it differs by its simpler, cubic form (pyrochlore forms octahedra). ## Crystal Forms This mineral forms exclusively simple, single crystals in the shape of a cube.

Geological environment

## Genesis It likely forms in the late stages of hydrothermal processes associated with carbonatite intrusions. It crystallizes from solutions rich in sodium and niobium within voids and fractures in the host rock. ## Mineral Associations Pauloabibite co-occurs with other minerals found in the Seis Lagos carbonatite, such as goethite, hematite, anatase, diaspore, gorceixite, fluorencite-(Ce) and -(Nd), and monazite-(Nd). ## Localities The only confirmed occurrence (type locality) of this mineral in the world is the Seis Lagos carbonatite complex, located in the municipality of São Gabriel da Cachoeira, in Amazonas State, Brazil.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of pauloabibite specimens is primarily assessed based on the sharpness and perfection of the cubic crystal form. Specimens with clearly developed, undamaged crystals, contrastingly set on the rock matrix, are most valued. Crystal size, although always microscopic, is also important – larger cubes (approaching 0.2 mm) are more desirable. The presence of several crystals on a single rock fragment enhances its attractiveness. ## Popular Localities The only source of specimens is the type locality in Seis Lagos, Brazil, which makes them extremely difficult to acquire on the collector's market.

Care and storage

## Cleaning Pauloabibite specimens are extremely small and delicate. Any mechanical cleaning should be avoided. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. The use of water or any chemicals is not recommended. ## What to Avoid Contact with acids and other chemical agents must be strictly avoided. The crystals are brittle, so they should be protected from impacts, scratching, and vibrations. The specimen should not be exposed to sudden temperature changes. ## Storage Specimens should be stored under stable conditions, in sealed "micromount" boxes, to protect them from dust and mechanical damage. It is best to keep them away from direct sunlight and heat sources.

Sources

IMA Mineral List (CNMNC)