Phosphosiderite | |
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![]() Red phosphosiderite between violet strengite. Picture width 4 mm. | |
General | |
Category | Phosphate minerals |
Formula (repeating unit) | Hydrated iron phosphate FePO4·2H2O |
IMA symbol | Phsd[1] |
Crystal system | Monoclinic |
Crystal class | Prismatic 2/m |
Space group | P21/n (no. 14) |
Unit cell | 454.76 ų |
Identification | |
Formula mass | 186.85 |
Color | Usually red to pink to purple, sometimes green, usually yellow veined |
Crystal habit | Tabular {010} or stout prismatic [001] |
Twinning | Common on {101}, typically as interpenetration |
Cleavage | {010} Distinct, {001} Indistinct |
Fracture | Uneven |
Mohs scale hardness | 3.5–4 |
Luster | Vitreous |
Streak | White |
Diaphaneity | Transparent, translucent |
Specific gravity | 2.74–2.76 |
Density | 2.74 – 2.76 measured, 2.76 calculated |
Optical properties | Biaxial (−) |
Refractive index | nα = 1.692 nβ = 1.725 nγ = 1.738 |
Birefringence | 0.046 |
Pleochroism | Visible |
2V angle | Measured: 62°, Calculated: 62° |
Dispersion | Very strong r > v |
Solubility | Totally soluble in hydrochloric acid, nearly insoluble in nitric acid |
Phosphosiderite is a rare mineral named for its main components, phosphate and iron. The siderite at the end of phosphosiderite comes from the word "sideros", the Greek word for iron. It was published in 1890, and has been a valid species since pre-IMA. It is an IMA approved mineral which got grandfathered, meaning its name is still believed to refer to an existing species.[2]
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