Raade, G., Ferraris, G., Gula, A., Ivaldi, G. &
Bernhard, F. (2002): Kristiansenite, a new calcium-scandium-tin sorosilicate
from granite pegmatite in Tördal, Telemark, Norway. Mineralogy and
Petrology, 75, 89-99.
Summary
Kristiansenite occurs as a late hydrothermal mineral in vugs in an amazonite
pegmatite at Heftetjern, Tørdal, Telemark, Norway. Tapering crystals,
rarely up to 2 mm long, are colourless, white, or slightly yellowish. The
mineral has the ideal composition Ca2ScSn(Si2O7)(Si2O6OH)
and is triclinic C1 with cell parameters a = 10.028(1), b
= 8.408(1), c = 13.339(2) Å, <alpha> = 90.01(1), <beta>
= 109.10(1), <gamma> = 90.00(1)°, V = 1062.7(3) Å3
(Z = 4). It has a monoclinic cell within \sim 0.1 Å and is polysynthetically
twinned on {010} by metric merohedry. The strongest reflections in the X-ray
powder pattern are [d in Å, (Iobs), (hkl)]:
5.18 (53) (1-11), 3.146 (100) (004), 3.089 (63) (-222), 2.901 (19) (221),
2.595 (34) (222), 2.142 (17) (-3-31). The Mohs' hardness is 5½-6;
Dcalc. = 3.64 g/cm3; only a mean refractive index of
1.74 could be measured. Scandium enrichment in the Heftetjern pegmatite and
the crystal chemistry of scandium are briefly discussed.