Ferriperbøeite-(La) (original) (raw)

RI values:

_n_α = 1.788(5) _n_β = 1.790(5) _n_γ = 1.810(5)

2V:

Measured: 40° (10), Calculated: 35°

δ = 0.022

Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.

Colour in reflected light:

dark grey

Comments:

nearly colourless in thin grains or pale brownish in thicker ones (X) to greenish-brown (Y, Z)

Crystal System:

Monoclinic

Class (H-M):

2/m - Prismatic

Cell Parameters:

a = 8.9458(2) Å, b = 5.7297(1) Å, c = 17.6192(3) Å
β = 115.950(2)°

Ratio:

a:b:c = 1.561 : 1 : 3.075

Unit Cell V:

812.05 ų (Calculated from Unit Cell)