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