Dyrnaesite-(La) a new hyperagpaitic mineral from the Ilímaussaq alkaline complex, South Greenland

TY - JOUR

T1 - Dyrnaesite-(La) a new hyperagpaitic mineral from the Ilímaussaq alkaline complex, South Greenland

AU - Rønsbo, Jørn G.

AU - Balic Zunic, Tonci

AU - Petersen, Ole V.

PY - 2017/2

Y1 - 2017/2

N2 - The new mineral, dyrnaesite-(La), is found in the Ilímaussaq alkaline complex, South Greenland. The holotype material originates from an arfvedsonite lujavrite sheet as an accessory mineral. Dyrnaesite-(La) is pale yellowish green, with no cleavage and an irregular fracture. Density is 3.68(2)/3.682 g/cm3 (measured/ calculated). It is biaxial, negative, 2Vα = 47(1)/48 (measured/calculated); α = 1.6226(5), β = 1.6852(10), γ = 1.6982(2); X = c, Y = a, Z = b. The average values of microprobe analyses are (wt.%) P2O5 37.17, SiO2 0.15, CaO 0.90, Na2O 20.06, La2O3 16.44, CeO2 20.23, Pr2O3 1.40, Nd2O3 3.47, Sm2O3 0.24, Dy2O3 0.06, Y2O3 0.06. The crystal structure was solved from single-crystal X-ray diffraction data. Dyrnaesite-(La) is orta;2.00(PO4)6, the simplified formula is Na8Ce4+ REE2(PO4)6. The crystal structure is related closely to that of vitusite-(Ce), but is distinct from it in several aspects. The five strongest lines of the powder X-ray diffraction pattern are (d Å, (I %), (hkl)); 6.57 (100) (101), 4.62 (40) (301, 230, 400), 3.50 (40) (331), 2.80 (86) (232, 402), 2.67 (54) (060,630).

AB - The new mineral, dyrnaesite-(La), is found in the Ilímaussaq alkaline complex, South Greenland. The holotype material originates from an arfvedsonite lujavrite sheet as an accessory mineral. Dyrnaesite-(La) is pale yellowish green, with no cleavage and an irregular fracture. Density is 3.68(2)/3.682 g/cm3 (measured/ calculated). It is biaxial, negative, 2Vα = 47(1)/48 (measured/calculated); α = 1.6226(5), β = 1.6852(10), γ = 1.6982(2); X = c, Y = a, Z = b. The average values of microprobe analyses are (wt.%) P2O5 37.17, SiO2 0.15, CaO 0.90, Na2O 20.06, La2O3 16.44, CeO2 20.23, Pr2O3 1.40, Nd2O3 3.47, Sm2O3 0.24, Dy2O3 0.06, Y2O3 0.06. The crystal structure was solved from single-crystal X-ray diffraction data. Dyrnaesite-(La) is orta;2.00(PO4)6, the simplified formula is Na8Ce4+ REE2(PO4)6. The crystal structure is related closely to that of vitusite-(Ce), but is distinct from it in several aspects. The five strongest lines of the powder X-ray diffraction pattern are (d Å, (I %), (hkl)); 6.57 (100) (101), 4.62 (40) (301, 230, 400), 3.50 (40) (331), 2.80 (86) (232, 402), 2.67 (54) (060,630).

KW - Faculty of Science

KW - dyrnaesite-(La),

KW - new mineral,

KW - optical properties,

KW - chemical analyses,

KW - X-ray data,

KW - vitusite,

KW - Ilímaussaq

U2 - 10.1180/minmag.2016.080.075

DO - 10.1180/minmag.2016.080.075

M3 - Journal article

SN - 0026-461X

VL - 81

SP - 103

EP - 111

JO - Mineralogical Magazine

JF - Mineralogical Magazine

IS - 1

ER -