Fluorarrojadite-(BaFe)

Chemical formula: Na₂CaBaFe₂+Fe₂+₁₃Al(PO₄)₁₁(PO₃OH)F₂

Fluorarrojadite-(BaFe) is a very rare mineral from the arrojadite group, a hydrated phosphate of sodium, calcium, barium, iron, and aluminum, distinguished by its complex chemical composition.

## Characteristics Fluorarrojadite-(BaFe) is a very rare mineral belonging to the arrojadite supergroup. It forms small, tabular or bladed crystals, typically occurring as radial or tangled aggregates. Its appearance is inconspicuous, and identification requires advanced analytical methods due to its complex chemical composition and similarity to other phosphates. ## Physical Properties This mineral has a hardness of approximately 5 on the Mohs scale. It has a vitreous luster and is translucent. The calculated density is about 3.63 g/cm³. ## Colors and Varieties Observed specimens range in color from dark green to almost black. No named varieties of this mineral have been distinguished. ## History and Name Fluorarrojadite-(BaFe) was first described in 2006 by Anthony R. Kampf, Mark A. Cooper, Frank C. Hawthorne, William B. Simmons, Alexander U. Falster, and Elizabeth F. Foord. Its name refers to its chemical composition: it indicates the dominance of fluorine (Fluor), its belonging to the arrojadite group (arrojadite), and the dominance of barium (Ba) and iron (Fe) in specific positions within the crystal structure. It was approved by the International Mineralogical Association (IMA) under number 2005-049. The type locality is the Palermo No. 1 mine in Groton, Grafton County, New Hampshire, USA. ## Uses Fluorarrojadite-(BaFe) has no industrial applications. Its significance is purely scientific and collectible, as a very rare and chemically complex phosphate.

Properties

Mohs hardness: 5
Luster: Vitreous
Streak: Pale green
Density: 3.63
Cleavage: Good on {001}
Fracture: Uneven
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Macroscopic identification of fluorarrojadite-(BaFe) is practically impossible. This mineral forms very small, dark green to black, bladed crystals in radial aggregates. Positive identification requires advanced analytical techniques, such as X-ray microanalysis (EDS/WDS) to determine chemical composition and X-ray diffraction (XRD) to confirm crystal structure. ## Distinguishing from Similar Minerals It can be confused with many other dark phosphates found in pegmatites, such as triphylite, arrojadite-(KFe), or other minerals from the arrojadite group. Differentiation relies solely on chemical analysis, which reveals the characteristic dominance of barium, iron, and fluorine in specific positions within its structure. ## Crystal Forms Crystals are typically very small, bladed or tabular, often flattened. They most commonly form radial or tangled aggregates, and less frequently occur as single, isolated crystals.

Geological environment

## Genesis Fluorarrojadite-(BaFe) is a pegmatitic mineral. It forms in complex, granitic pegmatites, in phosphate-rich zones, as a product of late-stage crystallization. Its presence indicates specific geochemical conditions, including high concentrations of barium, iron, and fluorine. ## Mineral Associations This mineral coexists with other phosphates typical of pegmatites. At the type locality (Palermo No. 1 mine), it was found in association with quartz, beryl, whitmoreite, jahnsite-(CaMnFe), mitrydite, and other minerals from the arrojadite group. ## Localities The only confirmed and described occurrence of fluorarrojadite-(BaFe) in the world is its type locality – the Palermo No. 1 mine in Groton, Grafton County, New Hampshire, United States.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, fluorarrojadite-(BaFe) is valued primarily for the mere fact of its confirmed presence in a collection. Specimens showing well-formed, even if small, crystalline aggregates that clearly stand out from the host rock (matrix) are highly prized. Association with other rare phosphates is also important. A key element of value is accompanying analytical documentation confirming the mineral's identification. ## Popular Localities The only source of specimens is the historic type locality – the Palermo No. 1 mine in New Hampshire, USA. Finding a new specimen of this mineral is an event of scientific significance.

Care and storage

## Cleaning It is recommended to clean only with a soft, dry brush to remove dust. Avoid water and any chemical agents that could react with the mineral. ## What to Avoid Avoid contact with acids, detergents, and ultrasonic cleaners. The mineral may be sensitive to sudden temperature changes. Do not expose it to prolonged strong sunlight. ## Storage Specimens should be stored in stable conditions, in a dry place, preferably in a sealed display box, to protect them from dust and mechanical damage. Due to its rarity, it is advisable to store it away from other minerals that could scratch it.

Sources

IMA Mineral List (CNMNC)