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Eosphorite

Discovered in 1878; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Mn²⁺Al(PO₄)(OH)₂ • H₂O

Hydrated Manganese Aluminum Phosphate Hydroxide

Molecular Weight:

228.92 gm

Composition:

Manganese

24.00 %

Mn

30.99 %

MnO

Aluminum

11.79 %

Al

22.27 %

Al₂O₃

Phosphorus

13.53 %

P

31.00 %

P₂O₅

Hydrogen

1.76 %

H

15.74 %

H₂O

Oxygen

48.92 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Phosphates

Strunz 8th Ed. ID:

7/D.14-20

Nickel-Strunz 10th Ed. ID:

8.DD.20

8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H₂O
D : With only medium-sized cations, (OH, etc.):RO₄= 2:1

Related to:

Childrenite-Eosphorite Series. The Mn2+ analogue of Childrenite. Isostructural with Childrenite.

Varieties:

None

Synonyms:

None

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

Typically as crystals, short to long prismatic on [001], to 20 cm; in planar radial or spherical radiating groups, with wedge-shaped terminations; globular, rarely massive.

Twinning:

Twinning: May show twinning on {100} and {001}, observed optically, to give pseudo-orthorhombic symmetry; perhaps due to oxidation. 

Physical Properties

Cleavage:

Poor on {100}

Fracture:

Irregular/uneven, sub-conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.0

Density:

3.06 - 3.08 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Soluble in acids.

Optical Properties

Color:

Pink to rose-red, commonly brown to black when oxidized

Transparency:

Transparent to translucent

Luster:

Vitreous to resinous

Refractive Index:

1.628 - 1.679  Biaxial ( - )

Birefringence:

0.029 - 0.035

Dispersion:

Strong; r < v

Pleochroism:

Visible; X= yellow, Y= pink, Z= pale pink to colorless

Occurances

Geological Setting:

Typically a secondary mineral in some phosphate-bearing granite pegmatites.

Common Associations:

Rhodochrosite, lithiophilite, triploidite, dickinsonite (Branchville, Connecticut, USA); albite, cookeite, apatite, beryllonite, hydroxyl-herderite, tourmaline (Newry, Maine, USA).

Common Impurities:

Fe

Type Locality:

Fillow Quarry (Branchville Quarry; Branchville Mica Mine; Smith Mine), Branchville, Redding (Reading), Fairfield Co., Connecticut, USA

Year Discovered:

1878

View mineral photos:

Eosphorite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Eosphorite is a rare phosphate mineral that is isostructural with, and forms a solid solution series with, Childrenite. Eosphorite is also the manganese (Mn) analogue of Childrenite. Eosphorite is rich in manganese while Childrenite is rich in iron. Eosphorite is typically found in hues of pink and orange and Childrenite is yellowish to orangish brown to dark brown.

Eosphorite gems are fairly rare and a very attractive collector's gem but a bit too soft for jewelry. Eosphorite gems are typically slightly to heavily included since clean crystals are very rare.

Eosphorite was named in 1878 by American mineralogist George Jarvis Brush (1831 - 1912) and American mineralogist Edward Salisbury Dana (1849 - 1935) from the Greek word έωσφορος meaning dawn-bearing, in allusion to the pink and orange colors.

Eosphorite distribution: in the USA, from Branchville, Fairfield County, Connecticut; at a number of places around Newry, in the Red Hill and Black Mountain quarries, Rumford, Oxford County, and elsewhere in Maine; in the Hugo mine, 1.5 km south of Keystone, Pennington County, South Dakota; from the Foote mine, near Kings Mountain, Cleveland County, North Carolina; in the White Picacho district, Maricopa and Yavapai Counties., Arizona. At Hagendorf, Bavaria, and on the Greifensteine, near Ehrenfriedersdorf, Saxony, Germany. In the Viitaniemi pegmatite, Eräjärvi, Finland. In Brazil, large crystals from the Lavra da Ilha pegmatite, in the Jequitinhonha River, three km north of Taquaral; in the Sapucaia pegmatite mine, about 50 km east-southeast of Governador Valadares; at the João Modesto dos Santos mine, and from a number of other mines around Linópolis and Mendes Pimental, Minas Gerais, Brazil. From Wycheproof, Victoria, Australia.

Eosphorite gems for sale: