Earlandite
Earlandite, [Ca3(C6H5O7)2(H2O)2]·2H2O, is the mineral form of calcium citrate tetrahydrate. It was first reported in 1936 and named after the English microscopist and oceanographer Arthur Earland FRSE. Earlandite occurs as warty fine-grained nodules ca. 1 mm in size in bottom sediments of the Weddell Sea, off Antarctica. Its crystal symmetry was first assigned as orthorhombic, then as monoclinic, and finally as triclinic.
| Earlandite | |
|---|---|
| General | |
| Category | Organic minerals |
| Formula (repeating unit) | [Ca3(C6H5O7)2(H2O)2]·2H2O |
| IMA symbol | Ear |
| Strunz classification | 10.AC.15 |
| Crystal system | Triclinic |
| Space group | P1 (No. 2) |
| Unit cell | a = 5.9466(4), b = 10.2247(8) c = 16.6496(13) [Å]; Z = 2 |
| Identification | |
| Color | White, pale yellow |
| Crystal habit | Nodular |
| Streak | White |
| Diaphaneity | Transparent |
| Specific gravity | 1.80–1.95 (measured), 2.00 (calculated) |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.515 nβ = 1.530 nγ = 1.580 |
| Birefringence | δ = 0.065 |
| 2V angle | 60° |
| Diagnostic features | Fine-grained and wart-like nodule crystal habit |
| Solubility | Insoluble |
| References | |
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