Lanthanite
Lanthanites are a group of isostructural rare earth element (REE) carbonate minerals. This group comprises the minerals lanthanite-(La), lanthanite-(Ce), and lanthanite-(Nd). This mineral group has the general chemical formula of (REE)2(CO3)3·8(H2O). Lanthanites include La, Ce, and Nd as major elements and often contain subordinate amounts of other REEs including praseodymium (Pr), samarium (Sm), europium (Eu) and dysprosium (Dy). The lanthanite crystal structure consists of layers of 10-fold coordinated REE-oxygen (O) polyhedra and carbonate (CO32−) groups connected by hydrogen bonds to interlayer water molecules, forming a highly hydrated structure.
| Lanthanite-(La), Lanthanite-(Nd), Lanthanite-(Ce) | |
|---|---|
Lanthanite-(Nd) from Mitsukoshi, Hizen-cho, Karatsu City, Saga Prefecture, Japan. | |
| General | |
| Category | Carbonate minerals |
| Formula (repeating unit) | (REE)2(CO3)3·8(H2O) |
| IMA symbol | Ltn |
| Strunz classification | 5.CC.25 |
| Dana classification | (La): 15.04.02.01 (Nd): 15.04.02.02 (Ce): 15.04.02.03 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Pbnb |
| Unit cell | a = 9.476(4)-9.483(6) b = 16.940(8)-16.938(11) c = 8.942(4)-8.965(3) [Å], Z = 4 |
| Identification | |
| Color | Pale pink to purple |
| Crystal habit | Platy |
| Twinning | Common on {101} |
| Cleavage | Micaceous, perfect on {101} |
| Fracture | Uneven |
| Tenacity | Sectile |
| Mohs scale hardness | 2.5 |
| Luster | Vitreous to pearly |
| Streak | White |
| Density | 2.78-2.84 (measured), 2.79-2.816 (calculated) |
| Optical properties | Biaxial (-) |
| 2V angle | 58-61° (measured), 60-63.5° (calculated) |
| References | |
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