Refractive Index	Mineral	Birefringence
from various sources	no guarantee	from various sources
1.370 - 1.470	Opal	0.000
1.378 - 1.390	Sellaite	0.012
1.420 - 1.430	Fire Opal	0.000
1.433 - 1.435	Fluorite (Ca)	0.000
1.460 - 1.570	Chrysocolla	0.023 - 0.050
1.461 - 1.485	Creedite	0.024
1.462 - 1.550	Lechatelierite	?
1.464 - 1.507	Thaumasite	0.039
1.473 - 1.502	Natrolite	0.012 - 0.013
1.475 - 1.492	Charlesite	0.017
1.479 - 1.493	Analcime	0.001 - 0.002
1.480 - 1.483	Hackmanite	0.000
1.480 - 1.483	Sodalite	0.000
1.480 - 1.540	Moldavite	0.000
1.485 - 1.519	Epistilbite	0.010
1.486 - 1.658	Calcite	0.154 - 0.174
1.488 - 1.505	Inderite	0.017
1.488 - 1.525	Kurnakovite	0.027 - 0.034
1.489 - 1.651	Whewellite	0.16
1.490 - 1.509	Yugawaralite	0.009
1.494 - 1.509	Hauyne	0.000
1.496 - 1.502	Tugtupite	0.006