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
All data from the card 18
- Category
- Organic minerals
- Formula
- [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
- 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
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