| 词条 | Kentbrooksite |
| 释义 |
| name = Kentbrooksite | category = Silicate mineral, Cyclosilicate | image = | imagesize = | alt = | caption = | formula = (Na,REE)15(Ca,REE)6Mn3Zr3NbSi25O74F2·2H2O (original form) | strunz = 9.CO.10 (10 ed) 8/E.23-20 (8 ed) | dana = 64.1.2.1 | system = Trigonal | class = Ditrigonal pyramidal (3m) H-M symbol: (3m) | symmetry = R3m | unit cell = a = 14.24, c = 30.03 [Å] (approximated); Z = 3 | color = Yellow-brown | colour = | habit = aggregates (anhedral to subhedral) | twinning = | cleavage = None | fracture = Uneven | tenacity = Brittle | mohs = 5-6 | luster = Vitreous | streak = White | diaphaneity = Transparent | gravity = | density = 3.10 (measured) | polish = | opticalprop = Uniaxial (-) | refractive = nω=1.63, nε=1.62 (approximated) | birefringence = | pleochroism = None | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = Pyroelectric | references = [1][2] }}Kentbrooksite is a moderately rare mineral of the eudialyte group,[1] with formula (Na,REE)15(Ca,REE)6Mn3Zr3NbSi[(Si9O27)2(Si3O9)2O2]F2·2H2O.[2] This extended formula shows the presence of cyclic silicate groups and dominance of Si at the M4 site, according to the nomenclature of the eudialyte group.[3] The characteristic features of kentbrooksite, that make it different from eudialyte are: (1) dominancy of fluorine (the only currently known example among the whole group[1]), (2) dominancy of manganese, and (3) dominancy of niobium. Trace hafnium and magnesium are also reported.[2] Kentbrooksite is relatively common when compared to most other species of the group.[1] OccurrenceKentbrooksite was found in alkaline pegmatites within pulaskites of the Kangerdlugssuaq intrusion in East Greenland.[2] Notes on chemistryRare earth elements (REE) in kentbrooksite are dominated by cerium and yttrium. Potassium, strontium, iron, aluminium, titanium, magnesium are present as other admixtures. An important fraction of fluorine is substituted by chlorine and hydroxyl groups. References1. ^1 2 3 Mindat, Kentbrooksite, http://www.mindat.org/min-7132.html {{silicate-mineral-stub}}2. ^1 2 3 Johnsen, O., Grice, J.D., and Gault, R.A., 1998. Kentbrooksite from the Kangerdlugssuaq intrusion, East Greenland, a new Mn-REE-Nb-F end-member in a series within the eudialyte group: Description and crystal structure. European Journal of Mineralogy 10(2), 207-220. 3. ^Johnsen, O., Ferraris, G., Gault, R.A., Grice, D.G., Kampf, A.R., and Pekov, I.V., 2003. The nomenclature of eudialyte-group minerals. The Canadian Mineralogist 41, 785-794 7 : Cyclosilicates|Sodium minerals|Calcium minerals|Manganese minerals|Zirconium minerals|Niobium minerals|Trigonal minerals |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。