Childrenite
| Childrenite | |
|---|---|
Childrenite from Galileia, Minas Gerais, Brazil 2 cm across
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| General | |
| Category | Phosphate minerals |
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Formula (repeating unit) |
(Fe2+,Mn2+)AlPO4(OH)2·H2O |
| Strunz classification | 8.DD.20 |
| Crystal system | Orthorhombic |
| Crystal class | Pyramidal (mm2) (same H-M symbol) |
| Space group | Bba2 |
| Unit cell | a = 10.41 Å, b = 13.42 Å, c = 6.92 Å; Z = 8 |
| Identification | |
| Color | Yellowish brown, brown, clove-brown; colorless in transmitted light. |
| Cleavage | Poor/indistinct on {100} |
| Fracture | Irregular/uneven, sub-conchoidal |
| Mohs scale hardness | 5 |
| Luster | Vitreous, resinous |
| Streak | White |
| Diaphaneity | Transparent, translucent |
| Specific gravity | 3.11 - 3.19 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.644 - 1.649 nβ = 1.662 - 16.830 nγ = 1.671 - 1.691 |
| Birefringence | δ = 0.027 - 0.042 |
| Pleochroism | Visible |
| 2V angle | Measured: 40° to 45°, calculated: 50° |
| Dispersion | r > v strong |
| Solubility | Soluble in acids. |
| References | |
Childrenite is a rare hydrated phosphate mineral with elements iron, manganese, aluminium, phosphorus, oxygen and hydrogen. Its chemical formula is (Fe,Mn)AlPO4(OH)2 • H2O and it has a molecular weight of 229.83 g/mol. Its specific gravity is 3.2 and it has a Mohs hardness of 4.5 to 5. It is usually translucent and non-fluorescent, with imperfect cleavage. It has a vitreous lustre with a white streak, and is brown or yellow in color. It has a conchoidal, uneven fracture, and an orthorhombic crystal system.
Childrenite was discovered in 1823 by John George Children (1777–1852), who was a prominent English chemist and mineralogist. This secondary mineral was first found in the George and Charlotte Mine near in Devon. Its formation is probably from the alteration of granitic phosphates like lithiophilite and triphylite. Childrenite is also found in some ore veins.
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