Mineral	Refractive Index	Birefringence
no guarantee	from various sources	from various sources
Calcite	1.486 - 1.658	0.154 - 0.174
Carletonite	1.517 - 1.521	0.004
Carnelian	1.535 - 1.540	0.009
Cassiterite	1.997 - 2.098	0.103
Catapleiite	1.582 - 1.639	0.036
Cavansite	1.542 - 1.551	0.009 - 0.012
Celestine	1.619 - 1.635	0.009 - 0.010
Cerussite	1.804 - 2.079	0.271 - 0.273
Chalcedony	1.564 - 1.660	0.009
Chambersite	1.732 - 1.744	0.012
Charlesite	1.475 - 1.492	0.017
Charoite	1.545 - 1.560	0.007 - 0.009
Childrenite	1.649 - 1.691	0.027 - 0.042
Chkalovite	1.544 - 1.549	0.005
Chondrodite	1.592 - 1.646	0.027 - 0.032
Chrome Diopside	1.668 - 1.702	0.029
Chrysocolla	1.460 - 1.570	0.023 - 0.050
Chrysoprase	1.530 - 1.540	0.004
Citrine	1.543 - 1.554	0.009
Clinochlore	1.571 - 1.599	0.005 - 0.011
Clinohumite	1.625 - 1.675	0.028 - 0.029
Clinozoisite	1.670 - 1.734	0.005 - 0.015
Colemanite	1.586 - 1.614	0.028
Cordierite / Iolite	1.522 - 1.578	0.005 - 0.017
Creedite	1.461 - 1.485	0.024
Crocoite	2.290 - 2.660	0.350 - 0.370
Cuprite	2.848 - 2.849	0.000
Danburite	1.627 - 1.641	0.006 - 0.009
Datolite	1.621 - 1.675	0.044
Demantoid	1.880 - 1.889	0.000
Diamond	2.417 - 2.419	0.000
Diaspore	1.702 - 1.750	0.047 - 0.050
Diopside	1.664 - 1.730	0.030
Dioptase	1.644 - 1.720	0.051 - 0.053
Dolomite	1.679 - 1.681	0.179 - 0.181
Dravite	1.612 - 1.655	0.019 - 0.026
Dumortierite	1.678 - 1.723	0.027
Dunilite	1.677 - 1.718	0.030 - 0.041
Edenite	1.606 - 1.672	0.020 - 0.025
Ekanite	1.590 - 1.596	0.012
Elbaite	1.615 - 1.650	0.018 - 0.021
Emerald	1.560 - 1.605	0.005 - 0.009
Enstatite	1.650 - 1.680	0.007 - 0.020
Eosphorite	1.638 - 1.671	0.010 - 0.035
Epidote	1.715 - 1.797	0.012 - 0.049
Epistilbite	1.485 - 1.519	0.010
Euclase	1.650 - 1.677	0.019 - 0.025
Eudialyte	1.591 - 1.633	0.003 - 0.004
Fire Opal	1.420 - 1.430	0.000
Fluorite-Ca)	1.433 - 1.435	0.000
Fluornatromicrolite	2.030	0.000
Friedelite	1.625 - 1.664	0.003