Tranquillityite
Tranquillityite is silicate mineral with formula (Fe2+)8Ti3Zr2 Si3O24. It is mostly composed of iron, oxygen, silicon, zirconium and titanium with smaller fractions of yttrium and calcium. It is named after the Mare Tranquillitatis (Sea of Tranquility), the place on the Moon where the rock samples were found during the 1969 Apollo 11 mission. It was the last mineral brought from the Moon which was thought to be unique, with no counterpart on Earth, until it was discovered in Australia in 2011.
| Tranquillityite | |
|---|---|
| General | |
| Category | Silicate mineral (nesosilicate group) |
| Formula (repeating unit) | (Fe2+)8Ti3Zr2 Si3O24 |
| IMA symbol | Trq |
| Strunz classification | 9.AG.90 |
| Dana classification | 78.07.16.01 (Unclassified silicates) |
| Crystal system | Hexagonal Unknown space group |
| Unit cell | a = 11.69, c = 22.25 [Å] Z = 6; V = 2,633.24 Å3 |
| Identification | |
| Color | Gray, dark red-brown in transmitted light |
| Crystal habit | Lath shaped grains generally found as inclusions in other minerals or interstitial (<0.1% in weight) |
| Luster | Submetalic |
| Diaphaneity | Opaque to semitransparent |
| Density | 4.7 ± 0.1 g/cm3 |
| Optical properties | Biaxial |
| Refractive index | nα = 2.120 |
| Pleochroism | No |
| 2V angle | 40° |
| Common impurities | Y, Hf, Al, Cr, Nb, Nd, Mn, Ca |
| References | |
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