Mineral	Refractive Index	Birefringence
no guarantee	from various sources	from various sources
Gadolinite	1.780	0.050
Gahnite	1.790 - 1.818	0.000
Gahnospinel	1.730 - 1.800	0.000
Gaspeite	1.610 - 1.810	0.220
Genthelvite	1.742 - 1.745	0.000
Goergeyite	1.560 - 1.570	0.024
Goshenite	1.566 - 1.602	0.004 - 0.008
Grandidierite	1.583 - 1.639	0.037
Grossular	1.730 - 1.760	0.000
Hackmanite	1.483 - 1.487	0.000
Hambergite	1.553 - 1.628	0.072 - 0.074
Hauyne	1.494 - 1.509	0.000
Heliodor	1.566 - 1.579	0.004 - 0.007
Hematite	2.880 - 3.220	0.280
Hemimorphite	1.614 - 1.636	0.021 - 0.022
Herderite	1.587 - 1.627	0.029 - 0.030
Hessonite	1.742 - 1.748	0.000
Hibonite	1.790 - 1.807	?
Hiddenite	1.653 - 1.682	0.014 - 0.016
Hodgkinsonite	1.720 - 1.746	0.026
Hsianghualite	1.613	0.000
Huebnerite	2.170 - 2.320	0.120 - 0.130
Ilvaite	1.727 - 1.883	0.156
Imperial Topaz	1.605 - 1.640	0.008 - 0.016
Inderite	1.488 - 1.505	0.017
Inesite	1.609 - 1.644	0.035
Jadeite	1.640 - 1.667	0.012 - 0.020
Jasper	1.540	0.009
Jeremejevite	1.640 - 1.653	0.009 - 0.017
Johachidolite	1.712 - 1.726	0.008 - 0.014
Kornerupine	1.660 - 1.699	0.013 - 0.014
Kovdorskite	1.527 - 1.549	0.022
Kunzite	1.653 - 1.682	0.014 - 0.016
Kurnakovite	1.488 - 1.525	0.027 - 0.034
Kyanite	1.710 - 1.735	0.012 - 0.017
Labradorite	1.560 - 1.572	0.005 - 0.010
Lapis Lazuli	1.500 - 1.610	0.000
Larimar	1.595 - 1.645	0.028 - 0.038
Lawsonite	1.665 - 1.684	0.019 - 0.021
Lazulite	1.604 - 1.662	0.031 - 0.036
Lazurite	1.500	0.000
Lechatelierite	1.500 - 1.550	?
Legrandite	1.675 - 1.740	0.038 - 0.060
Leifite	1.512 - 1.522	0.010 - 0.011
Lepidolite	1.525 - 1.587	0.029 - 0.038
Leucite	1.508 - 1.511	0.001