Leucophosphite - Encyclopedia

Class : Phosphates, arsenates, vanadates
Subclass : Hydrated phosphates
Crystal system : Monoclinic
Chemistry : KFe₂(PO₄)₂(OH) 2H₂O
Rarity : Uncommon to fairly common

Leucophosphite is a relatively common secondary phosphate. It can form by replacement of primary phosphate minerals in many environments : granitic pegmatites, phosphorites, fluorapatite nodules in black shales, and also by reaction between guano and iron minerals. Its name comes from the Greek leukos (white) and phosphate in reference to its color and chemical composition. Leucophosphite crystals are rare, pseudo-orthorhombic prismatic, and often gathered in columnar aggregates. More commonly, leucophosphite occurs in lamellar or chalky masses. Its color is white to greenish or in different tones of brown and red-brown to purple.

Main photo : Leucophosphite from Puech de Leguo, La Capelle-Bleys, Villefranche-de-Rouergue, Aveyron, France © Jean-Marc Johannet

Leucophosphite from Tip Top Mine, South Dakota, USA © Jason B. Smith

Leucophosphite possibly twinned from Tip Top Mine, South Dakota, USA © Jason B. Smith

Leucophosphite from Echassières, Allier, France © Yannick Vessely

Leucophosphite in the World

Leucophosphite localities are quite numerous, but the best samples come from pegmatites. Superb 1 cm crystals, the most beautiful in the world, and centimeter-sized clusters come to us from the Tip-Top pegmatite (South Dakota), where they accompany rockbridgeite in alteration of triphylite nodules. Very beautiful crystals have also been extracted from the neighboring pegmatites of this state (Bull Moose, Gap Lode, White Elephant...), and that of Palermo (New Hampshire). Beautiful small crystals are known from Brazilian phosphate pegmatites, notably at Sapucaia, near Galiléia (Minas Gerais). Leucophosphite is also reported in various pegmatites from Portugal, Namibia and Madagascar. In its locality of discovery (Nighanboun Hills, Australia), this mineral occurs in veinlets of opal, variscite and chalcedony cutting serpentinite ; it would derive from the leaching of the guano which covers the rock.

Leucophanite in France

In France, leucophosphite is found at Echassières (Allier), at the Commanderie mine near Mauléon (Deux-Sèvres), at Chanteloube (Haute-Vienne) and at Villefranche-de-Rouergues (Aveyron).

Twinning

No twin officially known for this mineral species, but V-shaped crystals suggest the opposite.

Fakes and treatments

No fakes recorded for this mineral species.

Hardness : 3.5
Density : 2.948
Fracture : Undetermined
Streak : White

TP : Translucent to transparent
RI : 1.707 to 1.739
Birefringence : 0.032
Optical character : Biaxial +
Pleochroism : None
Fluorescence : None

Solubility : Sulfuric acid, hydrochloric acid

Magnetism : NoneRadioactivity : None

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