Mineral	Refractive Index	Birefringence
no guarantee	from various sources	from various sources
Magnesite	1.508 - 1.717	0.191
Malachite	1.655 - 1.999	0.254
Mandarin Garnet	1.780 - 1.810	0.000
Manganotantalite	2.140 - 2.340	0.015 - 0.020
Marialite	1.530 - 1.550	0.005 - 0.009
Meionite	1.550 - 1.600	0.034 - 0.040
Melanite	1.890 - 1.940	0.000
Mellite	1.510 - 1.530	0.028
Microlite	2.0 - 2.2	0.000
Milarite	1.529 - 1.551	0.003
Mimetite	2.129 - 2.144	0.019
Moldavite	1.480 - 1.540	0.000
Monazite-(Ce)	1.774 - 1.849	0.049 - 0.052
Montebrasite	1.570 - 1.620	0.020 - 0.050
Moonstone	1.528 - 1.537	0.007 - 0.008
Morganite	1.577 - 1.583	0.004 - 0.008
Mottramite	2.170 - 2.320	0.150
Musgravite	1.717 - 1.739	0.004 - 0.005
Nambulite	1.706 - 1.730	0.023
Narsarsukite	1.609 - 1.63	0.021 - 0.031
Natrolite	1.473 - 1.502	0.012 - 0.013
Nephrite	1.600 - 1.641	0.020
Neptunite	1.690 - 1.736	0.029 - 0.045
Nifontovite	1.575 - 1.584	0.009
Norbergite	1.563 - 1.59	0.026 - 0.027
Oligoclase	1.533 - 1.552	0.003 - 0.05
Olmiite	1.663 - 1.694	0.031
Oregon Sunstone	1.560 - 1.572	0.007 - 0.009
Orthoclase	1.518 - 1.525	0.005 - 0.012
Painite	1.787 - 1.816	0.027 - 0.029
Paraiba Tourmaline	1.610 - 1.650	0.018 - 0.040
Pargasite	1.63 - 1.65	0.020
Parisite	1.676 - 1.757	0.081
Pectolite	1.595 - 1.645	0.028 - 0.038
Peridot	1.650 - 1.703	0.035 - 0.038
Peristerite	1.525 - 1.536	0.008 - 0.010
Petalite	1.502 - 1.519	0.012
Pezzotaite	1.601 - 1.620	0.008 - 0.011
Phenakite	1.650 - 1.670	0.015 - 0.017
Phosgenite	2.114 - 2.145	0.026
Phosphophyllite	1.594 - 1.621	0.021
Phosphosiderite	1.692 - 1.739	0.046
Piemontite	1.730 - 1.829	0.025 - 0.076
Poldervaartite	1.634 - 1.656	0.022
Pollucite	1.517 - 1.525	0.000
Poudretteite	1.510 - 1.532	0.016 - 0.021
Powellite	1.974 - 1.984	0.010
Prasiolite	1.530 - 1.540	0.009
Prehnite	1.610 - 1.669	0.020 - 0.035
Prismatine	1.669 - 1.684	0.013
Pyromorphite	2.049 - 2.059	0.010
Pyrope	1.730 - 1.766	0.000
Pyroxmangite	1.726 - 1.764	0.016 - 0.020