Eosphorite
Eosphorite, Mn2+Al(PO4)(OH)2(H2O): pink to rose-red pegmatite phosphate, hardness 5, density 3.06 to 3.08, the manganese end of the childrenite series.
Eosphorite is a manganese aluminium phosphate, Mn2+Al(PO4)(OH)2(H2O) on the IMA list (G, 1878, USA), the manganese end of a series with childrenite. Pink to rose-red prisms to 20 cm, brown to black when oxidized; hardness 5, density 3.06 to 3.08. A 20.00 g piece reads 13.46 to 13.51 g in water, under childrenite’s 13.57 g.
In short
- Manganese end of the series. The September 2026 IMA-CNMNC Master List writes Mn2+Al(PO4)(OH)2(H2O); the Handbook of Mineralogy sheet says it forms a series with childrenite, the Fe2+ member. The sheet’s Buckfield, Maine analysis (MnO 29.94, FeO 1.38 wt%) works out at 95.6% manganese of the iron plus manganese atoms.
- The in-water gap. Weighed in water, a 20.00 g piece reads 20 − 20/D: 13.46 to 13.51 g on eosphorite’s measured 3.06 to 3.08, and 13.57 to 13.73 g on childrenite’s 3.11 to 3.19. No printed value falls in the 0.06 g between 13.51 and 13.57 g. Both sheets print hardness 5 and a white streak, so the balance is the simplest instrument here that separates them.
- Documented failure: colour. The name means dawn-bearing, for the pink. But the sheet says commonly brown to black when oxidized, and the International Gem Society says most eosphorites are usually brown. Childrenite is yellowish brown to brown. A brown crystal is not named by its colour.
- Documented failure: the printed 3.04. The ideal formula on the sheet’s own cell (V 977.9 ų, Z = 8) gives 3.110, not the printed D(calc.) 3.04; childrenite’s gives 3.170 against its printed 3.12 to 3.15. Neither sheet says what composition it used. This page weighs against the measured ranges only.
- Brazil and the gem question. The sheet names large crystals from the Lavra da Ilha pegmatite near Taquaral and the Sapucaia pegmatite mine in Minas Gerais. The International Gem Society eosphorite article says only Brazilian localities have yielded cuttable crystals, and cut stones are typically under 3 to 4 carats.
| Property | Eosphorite (sheet) | Childrenite (sheet) | Separates them? |
|---|---|---|---|
| IMA formula | Mn2+Al(PO4)(OH)2(H2O) | Fe2+Al(PO4)(OH)2(H2O) | Yes, by analysis |
| Analysis, Mn share of Fe + Mn | 95.6% (Buckfield, Maine) | 9.9% (Crinnis and Carlyon mine, Cornwall) | Yes |
| Density, measured | 3.06 to 3.08 | 3.11 to 3.19 | Yes, by 0.03 |
| 20.00 g piece in water | 13.46 to 13.51 g | 13.57 to 13.73 g | Yes: a 0.06 g gap |
| Density, printed D(calc.) | 3.04 | 3.12 to 3.15 | — |
| Density, ideal formula on the sheet’s cell | 3.110 | 3.170 | Does not reproduce either print |
| IGS specific gravity | 3.05 (pure Mn end member); 3.08 (Brazil) | 3.2 (pure Fe end member) | Consistent with the sheets |
| Colour | Pink to rose-red; commonly brown to black when oxidized | Yellowish brown to brown, clove-brown | No, when brown |
| Hardness; streak; cleavage | 5; white; {100}, poor | 5; white; {100}, poor | No |
| α refractive index | 1.628–1.644 | 1.644–1.649 | Touch at 1.644 |
| Dispersion | r less than v, strong | r greater than v, strong | Yes, near end-members (sheets) |
What is eosphorite? Formula and the manganese share
A manganese aluminium phosphate with water. The September 2026 IMA list gives Mn2+Al(PO4)(OH)2(H2O), status G, 1878, country USA, with the first reference in the American Journal of Science and Arts and a second in American Mineralogist 98 (2013), 1297. The Handbook of Mineralogy eosphorite sheet writes the same atoms with ·H2O and says it forms a series with childrenite. On standard atomic weights the ideal formula is 24.00% manganese, 11.79% aluminium and 13.53% phosphorus by mass, and reproduces the sheet’s ideal column: P2O5 31.00, Al2O3 22.27, MnO 30.99, H2O 15.74.
The Buckfield analysis. Scaled to one phosphorus, the sheet’s analysis from Buckfield, Oxford County, Maine gives Mn 1.002 and Fe 0.046: manganese 95.6% of the two. The International Gem Society eosphorite article calls eosphorite the Mn-dominant and childrenite the Fe-dominant member, and says high-manganese crystals may show an orange colour. The iron end is worked on the childrenite page.
Eosphorite or childrenite? The in-water gap
Hardness and streak do not separate them. Both sheets print hardness 5, streak white, cleavage {100} poor and the same pleochroism line. Density does. Eosphorite’s measured 3.06 to 3.08 reads 13.46 to 13.51 g for a 20.00 g piece in water; childrenite’s 3.11 to 3.19 reads 13.57 to 13.73 g. The 0.06 g between them is the in-water gap: a reading at 13.51 g or under is on the eosphorite side of the sheets, 13.57 g or over on the childrenite side. The method is on how to measure specific gravity at home.
Where the gap fails. Neither sheet prints a density for a mid-series crystal, and the childrenite sheet warns that the Fe:Mn ratio of its other localities should be confirmed. IGS says gemmy Brazilian crystals are Fe:Mn = 1:1. Such a crystal is exactly what the two printed ranges do not describe, so a reading inside the gap, or a cut stone near either edge, is a reason for an analysis, not a verdict. IGS adds that cuttable crystals are usually badly flawed and contain many inclusions.
The printed 3.04. The sheet’s cell (a 10.455, b 13.501, c 6.928 Å, β 90.0°, Z = 8) and the ideal formula give a calculated density of 3.110, above both the printed 3.04 and the measured 3.06 to 3.08. The same arithmetic on childrenite’s cell gives 3.170 against a printed 3.12 to 3.15. Neither sheet states the composition behind its D(calc.); the weighing above uses the measured values only.
What colour is eosphorite? Pink, peach or brown
Pink is the name; brown is common. The Handbook gives pink to rose-red, commonly brown to black when oxidized, and derives the name from the Greek for dawn-bearing, in allusion to the pink colour. IGS lists colourless, pale pink, pale yellow, light to dark brown, reddish brown, orange and black, and describes one cut stone from Taquaral as peachy orange. It says most eosphorites are brown and turn brown to black when oxidized. This page states no cause for any colour.
Crystal system: a documented disagreement. The Handbook sheet says monoclinic, pseudo-orthorhombic, space group P21/m with β 90.0°, and twinning on {100} and {001} observed optically. IGS says later studies placed eosphorite definitively in the orthorhombic system. Both are given, attributed; the IMA list’s second reference (American Mineralogist 98, 2013) has not been read for this page.
Where is eosphorite found? Brazil, Maine and Branchville
The sheet’s Distribution, in order. In the USA: Branchville, Fairfield County, Connecticut; places around Newry, the Red Hill and Black Mountain quarries, Rumford, and elsewhere in Maine; the Hugo mine near Keystone, South Dakota; the Foote mine near Kings Mountain, North Carolina; the White Picacho district, Arizona. Hagendorf and the Greifensteine, Germany. The Viitaniemi pegmatite, Finland. In Brazil, large crystals from the Lavra da Ilha pegmatite near Taquaral, the Sapucaia pegmatite mine, and the João Modesto dos Santos mine and others around Linópolis and Mendes Pimental, Minas Gerais. Wycheproof, Victoria, Australia.
No type locality is marked. The sheet gives type material at Yale University, New Haven, and the IMA list gives the country as USA; neither names the place. See what is a type locality. Typically a secondary mineral in phosphate-bearing granite pegmatites, its associates at Branchville are rhodochrosite, lithiophilite, triploidite and dickinsonite, and at Newry albite, cookeite, apatite, beryllonite, hydroxyl-herderite and tourmaline. Hagendorf, the Greifensteine and the João Modesto dos Santos mine area are on the childrenite sheet too. Other species are in the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.