eosphorite

(mineralogy) (Mn,Fe)Al(PO₄)(OH)₂·H₂O A usually rose-pink mineral composed of hydrous aluminum manganese phosphate, found massive or in prismatic crystals.

Environment

Late-mineral ore veins and a pegmatite phosphate (probably primary).

Two completely distinct types; one consisting of large, pink, well-formed (though usually corroded or altered) crystals; the other sheaves of subparallel crystals and radiating sprays of the bundles, with rough, very dark terminations. Vein crystals sharper, but usually small and dark.

Salmon pink, light to dark brown, gray, and almost black. Luster glassy (to pearly on the front face of the brown bundles); hardness 4Ɖ; specific gravity 3.06-3.25; fracture conchoidal; cleavage front and side pinacoid. Brittle; translucent to transparent.

Hydrous alkaline iron and manganese aluminum phosphate, forming an isomorphous series (MnO-FeO 31%, Al ₂ O 22%, P ₂ O ₅ 31%, and H ₂ O 16%). In my experience, though they form an isomorphous series, the pegmatite occurrences are wholly unlike the small crystals in the ore veins, and the large pink eosphorites bear little superficial resemblance to the much more frequent dark brown ones.

On heating, both types swell and lose weight and are easily crushed to powder. Brown material turns black and becomes magnetic. Pink variety turns buff color and is but weakly magnetic.

The brown sprays are distinctive in a pegmatite environment, though they resemble some stilbites in appearance. The pink crystals resemble nothing else in such an environment but hureaulite, which fuses easily into an orange-brown sphere.

This series has come due for restudy since the discovery of unique large salmon pink (but corroded, or even altered completely to limonite) crystals in Minas Gerais, Brazil. Brown sprays--like some from Branchville, Connecticut, and several of the New Hampshire and Maine pegmatites--contain more iron. Perhaps the proper name for the browner material should be childrenite rather than the eosphorite it has always been called. The Brazilian rose quartz crystal locality, Taquaral, has fine sprays of the brown crystals, some even on the rose quartz itself. They seem fresher, later, and perhaps more of a secondary mineral than the larger corroded pink crystals. On simple inspection one would not suspect the two types to belong to the same species, for they seem so very different. Bolivian childrenite crystal crusts are made up of very small individual crystals and are dark gray. Childrenite from Cornwall occurs as sparsely scattered, small, bright brown, rather equidimensional crystals. With so tremendous a habit variation in this series--almost too unlike for members of one series--it seems difficult to believe that they are truly completely isomorphous.

The brown crystals and sprays of Taquaral can be 1ƈ in. (about 3 cm) long, whereas the pink crystals are as much as 2-2Ɖ in. (5-7.5 cm) long and Ɖ in. (1 cm) across.