Hureaulite , Reddingite Locality: Cigana claim (Jocão claim), Galiléia , Doce valley, Minas Gerais , Southeast Region, Brazil ( Locality at mindat.org ) Size: 5.9 x 4.9 x 3.9 cm. This pegmatite is known for its suite of high-quality phosphate species, more than for gem crystals. It is very similar, in fact, to the famous Tip Top Mine in South Dakota for the major phosphate species found. However, hureaulite from this locality has a more beautiful, intense rich color and lustre, and is arranged in such pretty aggregates against contrasting lustrous brown reddingite, that I consider these to be among the more beautiful examples of the species. Usually you find the hureaulite dispersed as a flat carpet of small 2-5mm crystals on matrix shards. Few specimens have relief and well-defined aesthetics: but this piece has a sharp, superb cluster approximately 3 cm tall perched atop the specimen. It is 3-dimensional and leaps out. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Hureaulite
A manganese phosphate named in 1826 for its type locality, Les Hureaux in Haute-Vienne, France.
Intro adapted from Wikipedia (CC BY-SA).
Hureaulite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Mn²⁺₅(PO₃OH)₂(PO₄)₂·4H₂O.
It crystallizes in the monoclinic crystal system (space group C2/c). It is a member of the Hureaulite structural group.
Key properties: Mohs hardness 3.5; specific gravity 3.15–3.19; Nearly white streak; Vitreous, inclined towards greasy luster; refractive index 1.653; optically biaxial.
IMA symbol Hur, IMA status: approved, named in 1825.
A late-stage secondary mineral produced through alteration of primary phosphates in complex granite pegmatites.
It is found associated with Lithiophilite, triphylite, heterosite, rockbridgeite, cacoxenite, vivianite, fairfieldite, dickinsonite, eosphorite, stewartite, strengite, phosphosiderite.
The name refers to its first-noted occurrence near Huréaux, France.