TABLE 407 



INDEX OF REFRACTION 

 Selected Biaxial Minerals 



367 



The values are arranged in the order of increasing index of refraction and are for the sodium D line except where 

 noted. Selected by Dr. Edgar T. Wherry from private compilation of Dr. Esper S. Larsen of the U. S. Geological 



Survey. 



Mineral. 



Formula. 



Index of refraction. 



»{3 



(a) Biaxial Positive Minerals. 



Stercorite 



Aluminite 



Tridymite 



Thenardite 



Carnallite 



Alunogenite. . . . 

 Melanterite .... 



Natrolite 



Arcanite 



Struvite 



Heulandite 



Thomsonite .... 

 Harmotomite. . . 



Petalite 



Monetite 



Newberyite .... 



Gypsum 



Mascagnite 



Albite 



Hydromagnesite 



Wavellite 



Kieserite 



Copiapite 



Whewellite 



Variscite 



Labradorite .... 



Gibbsite 



Wagnerite 



Anhydrite 



Colemanite 



Fremontite 



Vivianite 



Pectolite 



Calamine 



Chondrodite. . . . 



Turquois 



Topaz 



Celestite 



Prehnite 



Barite 



Anthophyllite . . 



Sillimanite 



Forsterite 



Enstatite 



Euclasite 



Triplite 



Spodumenite . . . 



Diopside 



Olivine 



Triphylite 



Na 2 0. (NH4)20.P 2 05.oH 2 



Al2O3.SO3.9H2O 



Si0 2 



Na 2 O.S03 



KCl.MgCl2.6H2O 



AI2O3.3SO3.16H2O 



FeO.SO3.7H2O 



Na2O.Al2O3.3SiO2.2H2O 



K2O.SO3 



(NH4)20.2MgO.P 2 05.i2H 2 



CaO.Al2O3.6SiO2.3H2O 



(Na 2 , Ca)O.A!203.2Si0 2 .3H 2 



(K2, Ba)O.Al203.sSi0 2 .^H 2 



Li2O.Al2O3.8SiO!. 



2CaO.P2O5.H2O 



2MgO.P2O5.7H2O 



CaO.SO3.2H2O 



fNH4) 2 G.SQj 



"Ab" = Na2O.AI2O3.6SiO:> 



4MgO.3CO2.4H2O 



3A1 2 03.2P205.I2(H 2 0, 2HF) 



MgO.SO3.H2O 



2Fe 2 3 .5SO3.i8H20 



CaO.C2O3.H2O 



Al2O3.P2O5.4H2O 



Ab2An3 



AI2O3.3H2O 



3MgO.P2O5.MgFi! 



CaO.SOs 



2CaO.3B2O3.5H2O 



Na20.Al20 3 .P205.(H 2 0, 2HF) 



3FeO.P 2 05.8H 2 



Na20. 4 Ca0.6Si0 2 .H 2 



2ZnO.Si0 2 .H 2 



4 Mg0.2Si0 2 .Mg(F, 0H) 2 



CuO.3Al2O3.2P1-O5.oH2O 



2A10F.Si0 2 



SrO.SOs 



2CaO.Al 2 3 .3Si0 2 .H 2 



BaO.SOs 



MgO.SiO?. 



Al 2 3 .Si0 2 



2MgO.Si0 2 



MgO.Si0 2 



2BeO.Al2O3.2SiO2.HiiO 



3MnO.P5.O5.MnF2 



Li20.Al20 3 .4Si0 2 



CaO.Mg0.2Si0 2 



2(Mg, Fe)O.Si0 2 



Li 2 0.2(Fe,Mn)O.P 2 Os 



1.469 

 1.470 



1-473 

 I 485 

 1.494 

 1.483 

 1.486 

 1-493 

 1.497 

 l-5°4 

 I -5°5 

 I-S2S 

 1.508 

 I. 516 

 1-525 

 1-533 

 1 -530 

 1-533 

 1-536 

 1-54° 

 1-552 

 1.586 

 1-595 

 1650 

 1.582 

 1.568 

 I-587 

 1.582 

 1. 614 



1. 614 



1. 615 

 1-633 

 1-634 

 1.636 

 1.639 

 1.650 

 1.627 

 1. 631 

 1.649 

 1.648 

 1-657 

 1-653 

 1.670 

 1.658 

 1. 671 

 1.672 

 1.676 

 1.694 

 1.699 

 1.692 



Smithsonian Tables. 



