Illoqite-(Ce), Na2NaBaCeZnSi6O17, a new member of the nordite supergroup from Ilímaussaq alkaline complex, South Greenland.

Abstract The new mineral, illoqite-(Ce), with the ideal formula Na 2 NaBaCeZnSi 6 O 17 , has been discovered in Taseq Slope, Ilímaussaq Alkaline Complex, Southern Greenland. Illoqite-(Ce) occurs a hyperalkaline ussingite vein closely related to one of largest veins complex. associated minerals are aegirine, arfvedsonite, britholite-group epistolite, chkalovite, lueshite, Mn-rich pectolite group member and steenstrupine-(Ce). crystallises as either single euhedral crystals up 150 μm size or radiating aggregates consisting few many crystals. 200 diameter. can occur scattered small groups aggregates, but sometimes they high concentrations creating clusters bands almost completely illoqite-(Ce). empirical on basis anions is 2.00 1.00 (Ba 0.59 Sr 0.32 Ca 0.04 0.03 ) Σ0.98 (Ce 0.68 La 0.31 Nd 0.09 Pr Σ1.12 (Zn 0.42 Fe 0.34 Li 0.14 Mn Σ0.99 Si 5.97 simplified being Na(Ba,Sr)(Ce,La,Nd)(Zn,Fe,Li)Si . exhibits sector zoning between elements Ba. crystal structure was determined using single-crystal X-ray diffraction data refined R 1 = 2.46% 1902 unique reflections. orthorhombic, Pcca 14.5340(7), b 5.2213(1), c 19.8270(4) Å, V 1507.25(6) Å 3 Z 4. strongest lines powder pattern [ d ( I %) hkl )] are: 7.266 (79) (200), 4.688 (44) (104), 4.241 (64) (210), 3.486 (114), 3.340 (52) (312), 2.986 (67) (410), 2.882 (100) (314) 2.789 (016). nordite supergroup named after Greenlandic word illoq, meaning cousin, allusion mineral's close relation nordite-(Ce).