Fulbrightite

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

A hydrated vanadium oxyarsenate of calcium, forming microscopic, olive-green crystals, known only from one locality in the world.

## Characteristics Fulbrightite is a very rare secondary mineral from the arsenate group. It forms small aggregates composed of platy or isometric crystals, rarely exceeding 0.2 mm in size. It often occurs as hollow epimorphs (crusts) after earlier, dissolved minerals, especially calcite crystals. Its most characteristic visual feature is an intense, olive-green or yellow-green color. ## Physical Properties Fulbrightite crystals are translucent and exhibit a vitreous luster, locally transitioning to greasy. The mineral's hardness on the Mohs scale is approximately 3. Its density, calculated based on chemical composition and crystal structure, is 3.13 g/cm³. ## Colors and Varieties This mineral occurs in uniform shades, from dark olive-green to lighter, yellow-green. No color varieties or commercial varieties have been distinguished. ## History and Name Fulbrightite was described as a new mineral species in 2011 by Anthony R. Kampf and his team. The name honors James William Fulbright (1905–1995), an American senator who was the founder of the prestigious scientific exchange program (Fulbright Program). The mineral was discovered at the Getchell mine in Nevada, USA. ## Applications Due to its extreme rarity and microscopic crystal sizes, fulbrightite has no industrial application. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of micromount minerals.

Properties

Mohs hardness
3
Luster
Vitreous to Greasy
Streak
Light green
Density
3.13
Cleavage
Good on {001}
Transparency
Translucent
Crystal system
Tetragonal

Diagnostic features

## Identification Identifying fulbrightite is extremely difficult and impossible without specialized equipment. Preliminary identification based on visual characteristics requires the use of a stereoscopic microscope. Key features include olive-green color, platy crystal habit forming aggregates, and co-occurrence with minerals from the Getchell mine. Final confirmation requires advanced analytical methods such as X-ray diffraction (XRD) or chemical microanalysis (EDS/WDS). ## Distinguishing from Similar Minerals This mineral can be confused with other green, secondary arsenates or vanadates occurring in the same locality, such as bidenbaughite. Definitive differentiation is only possible based on analysis of its crystal structure and chemical composition. ## Crystal Forms Fulbrightite forms aggregates of small, platy crystals with a habit dominated by a flat basal pinacoid {001}. Crystals can also be isometric. Characteristic are hollow overgrowths and crusts (epimorphs) after other minerals.

Geological environment

## Genesis Fulbrightite is a secondary mineral, forming in the oxidation zone of an ore deposit. Its genesis is associated with low-temperature hydrothermal processes that lead to the alteration of arsenic sulfides – realgar and orpiment. It occurs within carbonized shear zones in sedimentary rocks. ## Mineral Associations This mineral occurs in association with other rare arsenic and vanadium minerals. Its most important associations include: getchellite, orpiment, realgar, bidenbaughite, laffittite, guettardite, and unidentified vanadium-arsenic phases. ## Localities The only confirmed locality of fulbrightite in the world is its type locality – the Getchell mine, Potosi district, Humboldt County, Nevada, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria For micromount collectors, specimens with well-formed, sharp crystals of good luster and intense color are of the highest value. Rich crystal aggregates and specimens where fulbrightite co-occurs with other rare minerals typical of this locality, such as getchellite, are particularly prized. ## Popular Localities The only source of fulbrightite specimens is the Getchell mine in Nevada. Material from this locality is extremely difficult to obtain and commands high prices in the specialized collector's market.

Care and storage

## Cleaning Fulbrightite specimens should only be cleaned dry, using a soft brush or a stream of compressed air from a safe distance. Contact with water is unacceptable. ## What to Avoid Contact with water and other liquids must be strictly avoided, as it is a hydrated mineral and can be damaged. It is sensitive to high temperatures and chemicals. Due to its arsenic content, the mineral is toxic – avoid inhaling dust and wash hands after each contact. ## Storage It is recommended to store specimens in tightly sealed "micromount" boxes, which protect them from mechanical damage, dust, and moisture. They should be kept in a stable, dry environment, away from direct sunlight and heat sources.

Sources

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