Merrillite
Merrillite is a calcium phosphate mineral with the chemical formula Ca9NaMg(PO4)7. It is an anhydrous, sodic member of the whitlockite group.[3]
| 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 | [1][2][3] |
Discovery and naming
The mineral is named after George P. Merrill (1854–1929) of the Smithsonian Institution.[3] 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.[3]
Occurrence
Merrillite is a very important constituent of extraterrestrial rocks. It occurs in pallasites, lunar rocks, martian meteorites, and many other meteorite groups.[4]
gollark: > Because in Michigan, those particular cities usually decide the votes due to their high population. I'm going to call it "favouring rural people" if they get more voting power than they would if it was proportional to actual population.
gollark: You could also call that a "representative democracy", but I don't think disputing definitions is helpful.
gollark: Are you saying that the electoral college system does *not* favour rural people over city ones, in general?
gollark: There are a lot of groups of people with different needs. Why favour rural people over city people instead of rich people over poor people or [race 1] over [race 2] or Apple users over Android users or whatever? It's arbitrary.
gollark: Please stop contradicting yourself on this, as it is very annoying.
References
- Mineralienatlas
- Merrillite data on Webmineral
- "Merrillite". Mindat. Retrieved 6 January 2013.
- Jolliff, Bradley L.; John M. Hughes; John J. Freeman & Ryan A. Zeigler (2006). "Crystal chemistry of lunar merrillite and comparison to other meteoritic and planetary suites of whitlockite and merrillite". American Mineralogist. 91: 1583–1595. doi:10.2138/am.2006.2185.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.