Merrillite
| Merrillite | |
|---|---|
| General | |
| Category | Phosphate mineral |
|
Formula (repeating unit) |
Ca9NaMg(PO4)7 |
| Strunz classification | 8.AC.45 |
| Crystal system | Trigonal |
| Crystal class | Ditrigonal pyramidal (3m) (same H-M symbol) |
| Space group | R3c |
| Unit cell | a = 10.362 Å, c = 37.106 Å; Z = 6 |
| Identification | |
| Color | Colorless to white |
| Crystal habit | Occurs as anhedral grains |
| Cleavage | Poor - indistinct |
| Tenacity | Brittle |
| Luster | Vitreous |
| Specific gravity | 3.1 (measured) |
| Optical properties | Uniaxial (-) |
| Refractive index | nε=1.62, nω=1.623 |
| Birefringence | 0.0030 |
| References | |
Merrillite is a calcium phosphate mineral with the chemical formula Ca9NaMg(PO4)7. It is an anhydrous, sodic member of the whitlockite group.
The mineral is named after George P. Merrill (1854–1929) of the Smithsonian Institution. Merrill had described the mineral from four meteorites in 1915: the Alfianello, Dhurmsala, Pultusk, and Rich Mountain meteorites. The mineral was not recognized as distinct from whitlockite, however, by the IMA until 1975.
Merrillite is a very important constituent of extraterrestrial rocks. It occurs in pallasites, lunar rocks, martian meteorites, and many other meteorite groups.
...
Wikipedia