Childrenite
Childrenite, Fe2+Al(PO4)(OH)2(H2O): brown pegmatite phosphate, hardness 5, density 3.11 to 3.19, white streak, the iron end of a series with eosphorite.
Childrenite is an iron aluminium phosphate, Fe2+Al(PO4)(OH)2(H2O) on the IMA list (G, 1823, United Kingdom), and the iron end of a series with eosphorite. It forms brown, often doubly terminated crystals to 2 cm in granite pegmatites, hardness 5, density 3.11 to 3.19. The sheet’s Cornish analysis puts iron at 90.1% of iron plus manganese.
In short
- Iron end of a two-name series. The September 2026 IMA-CNMNC Master List writes Fe2+Al(PO4)(OH)2(H2O) for childrenite and Mn2+Al(PO4)(OH)2(H2O) for eosphorite; both Handbook of Mineralogy sheets say the two form a series. The International Gem Society childrenite article gives the dividing rule in five words: series to eosphorite if Mn exceeds Fe.
- The iron-share check. Worked in atoms per phosphorus from the sheet’s Crinnis and Carlyon mine analysis (FeO 28.56, MnO 3.11 wt%), iron is 0.943 and manganese 0.104: 90.1% iron. The sheet’s own reference list carries a Tavistock crystal described as the Ch89Eo11 term, 89% childrenite. The two British figures agree to about one percentage point.
- Where. Devon near Tavistock (Wheal Crebor, the George and Charlotte mine, Russell United mines, Wheal Betsy), Cornwall (Crinnis and Carlyon mine, Wheal Jane) and Scar Crag, Keswick, Cumbria lead the sheet’s Distribution; it adds Germany, Kosovo, Zimbabwe, New Hampshire, Yukon, Brazil, Bolivia and South Australia. It marks no type locality.
- Documented limit: the sheet’s own warning. The Distribution field ends: other localities are known; the Fe:Mn ratio however should be confirmed. Hardness (5), streak (white), cleavage ({100}, poor) and the pleochroism line are printed identically on both sheets, so a brown crystal is named by its chemistry, not by a scratch or a streak.
- Brazil and the gem question. Both sheets list the João Modesto dos Santos mine and mines around Linópolis and Mendes Pimental, Minas Gerais. The International Gem Society says gemmy Brazilian crystals there are Fe:Mn = 1:1, and that all cut childrenites are small. The Handbook says nothing about cutting.
| Formula or analysis | Source | FeO wt% | MnO wt% | P2O5 wt% | Fe per P | Mn per P | Iron share of Fe + Mn |
|---|---|---|---|---|---|---|---|
| Childrenite, Fe2+Al(PO4)(OH)2(H2O) | IMA list; sheet analysis (2), ideal | 31.26 | 0 | 30.88 | 1.000 | 0 | 100% |
| Crinnis and Carlyon mine, Cornwall | Childrenite sheet, analysis (1) | 28.56 | 3.11 | 29.92 | 0.943 | 0.104 | 90.1% |
| Tavistock, Devon | Childrenite sheet, reference (4): “Ch89Eo11 term” | — | — | — | — | — | 89% childrenite (as titled) |
| Buckfield, Maine | Eosphorite sheet, analysis (1) | 1.38 | 29.94 | 29.89 | 0.046 | 1.002 | 4.4% |
| Eosphorite, Mn2+Al(PO4)(OH)2(H2O) | IMA list; sheet analysis (2), ideal | 0 | 30.99 | 31.00 | 0 | 1.000 | 0% |
What is childrenite? Formula, series and the iron-share check
An iron aluminium phosphate with water. The September 2026 IMA list gives Fe2+Al(PO4)(OH)2(H2O), status G, 1823, country United Kingdom, first reference Quarterly Journal of Science, Literature, and the Arts 16 (1823), 274. The Handbook of Mineralogy childrenite sheet writes the same atoms with ·H2O. On standard atomic weights the ideal formula is 24.30% iron, 11.74% aluminium and 13.48% phosphorus by mass; the script reproduces the sheet’s ideal column exactly: P2O5 30.88, Al2O3 22.18, FeO 31.26, H2O 15.68.
The check. Divide each printed oxide by its formula weight and scale to one phosphorus. The Crinnis and Carlyon analysis gives Fe 0.943, Mn 0.104, Al 0.997, with Ca and Na about 0.03 each: iron is 90.1% of the iron plus manganese, a Fe:Mn ratio of about 9 to 1. The sheet’s reference (4), Giuseppetti and Tadini (1984), studied a Tavistock crystal it calls the Ch89Eo11 term of the childrenite–eosphorite series, which says the same thing for Devon.
Where the check stops. The IMA list does not print a boundary percentage. The International Gem Society’s childrenite article states the rule as series to eosphorite if Mn exceeds Fe, and its eosphorite article calls eosphorite the Mn-dominant and childrenite the Fe-dominant member. This page works the ratio; it does not restate IMA nomenclature it has not fetched. Formula-only scan: the IMA list has three rows of the pattern M2+Al(PO4)(OH)2·H2O, with Fe (childrenite), Mn (eosphorite) and Ca (foggite, 1973-067).
How do you tell childrenite from eosphorite?
By analysis, first. The two sheets print the same hardness (5), the same streak (white), the same cleavage ({100}, poor), the same fracture and the same pleochroism and orientation lines. Colour leans one way: childrenite yellowish brown to brown and clove-brown, eosphorite pink to rose-red but commonly brown to black when oxidized. Brown alone does not decide.
What the numbers add. Childrenite’s measured density, 3.11 to 3.19, is above eosphorite’s 3.06 to 3.08; dispersion is r greater than v on the childrenite sheet and r less than v on the eosphorite sheet, each for near end-member composition. Childrenite’s α, 1.644 to 1.649, starts where eosphorite’s ends. The weighing is set out on the eosphorite page and the method on how to measure specific gravity at home. The sheet’s closing line is the rule this page leans on: the Fe:Mn ratio should be confirmed.
Crystal system. The childrenite sheet says orthorhombic, probably monoclinic and pseudo-orthorhombic, with space group Bba2, and twinning on {100} and {001}, observed optically, that may be due to oxidation. The poor {100} cleavage is not a practical guide; see cleavage or fracture: how to tell.
Where is childrenite found? Devon, Cornwall and Brazil
British localities lead the sheet. The Distribution field reads: in England, from Devon, near Tavistock, at Wheal Crebor, the George and Charlotte mine, Russell United mines, Wheal Betsy, and many other places; from Cornwall, in the Crinnis and Carlyon mine, Wheal Jane, and elsewhere; from the Cobalt mine, Scar Crag, Causey Pike, Keswick, Cumbria. The IMA list gives the country of first description as the United Kingdom. The sheet marks no type locality; the term is explained on what is a type locality.
Then abroad. The Greifensteine near Ehrenfriedersdorf, Saxony, and Hagendorf, Bavaria; the Stari Trg mine (Trepča), Kosovo; the Fram pegmatite, Kamativi, and the Kondo pegmatite, Zimbabwe; the Palermo #1 mine, New Hampshire; the Rapid Creek–Big Fish River area, Yukon; large crystals at the João Modesto dos Santos mine and other mines around Linópolis and Mendes Pimental, Minas Gerais; the Siglo XX mine, Llallagua, Bolivia; and the Moculta phosphate quarry, South Australia.
Associates. At Tavistock the sheet names siderite, pyrite, apatite and quartz; on the Greifensteine zinnwaldite, tourmaline, apatite and kaolinite. It occurs in some complex granite pegmatites, typically as a low-temperature hydrothermal alteration product of primary phosphate minerals. Other iron and manganese phosphates on this site include strengite and phosphophyllite; the rest is in the species index.
Is childrenite a gemstone? What the sources say
Seldom, and small. The Handbook sheet is silent on gem use. The International Gem Society says all cut childrenites are small, that facetable crystals yield stones up to about 3 to 4 carats, and that cuttable material in the series is closer to the eosphorite end. It gives specific gravity 3.2 for the pure iron end member.
Documented failure: the Brazilian crystals. Both Handbook sheets list the same Brazilian mines, and IGS says the gemmy crystals from Minas Gerais are Fe:Mn = 1:1 and could be called childro-eosphorite. That name has no line on the September 2026 IMA list (whole-word script, 0 hits). At 1:1 the iron-share check gives 50%, exactly where IGS’s Mn-exceeds-Fe rule switches, so a Brazilian label reading either name needs an analysis behind it. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.