526 



TABLE 548.— INDEX OF REFRACTION OF SELECTED BIAXIAL MINERALS 



The values are arranged in the order of increasing j3 index of refraction and are for the 

 sodium D line except where noted. Selected by Edgar T. Wherry from private compilation 

 of Esper S. Larsen, of the U. S. Geological Survey. 



Biaxial positive minerals 

 Mineral Formula 



Stercorite Na 2 0-(NH4) 2 0-P 2 5 -9H,0 



Aluminite Al 3 GvSGv9H,0 



Tridymite Sid 



Thenardite Na.O-SO, 



Carnallite KCl-MgCl.-6H,0 



Alunogen A1 2 3 -3S0 3 -16H 2 



Melanterite FeO-S0 3 -7H 2 



Natrolite Na,0-Al 2 3 -3Si0 2 -2H 2 



Arcanite K 2 0-S0 3 



Struvite (NH«),0-2MgO-P,0.-12H,0 



Heulandite CaO-Al 2 0,-6SiGv3H 2 



Thomsonite (Na 2 , Ca)0- Al 2 3 -2Si0 2 -3H 2 



Harmotome (K,, Ba)0- Al 2 0,-5Si0 2 -5H 2 



Petalite Li 2 0-Al 2 3 -8Si0 2 



Monetite 2CaO ■ P 2 O s • H 2 



Newberyite 2MgO-P 2 0„-7H 2 



Gypsum CaO-SGv2H 2 



Mascagnite (NH 4 ) 2 0-SO, 



Albite "Ab" = Na 2 0-Al 2 Gv6Si0 2 



Hydromagnesite .. 4MgO-3CGv4H 2 



Wavellite 3Al 2 3 -2P 2 O s -12(H 2 0, 2HF) 



Kieserite MgO-SGvH 2 



Copiapite 2Fe 2 Gv5SGvl8H 2 



Whewellite CaO-C 2 3 H 2 



Variscite A1 2 3 ■ P 2 5 ■ 4H 2 



Labradorite Ab 2 An 3 



Gibbsite Al 2 Gv3H 2 



Wagnerite 3MgO-P 2 O s -MgF 2 



Anhydrite CaO • S0 3 



Colemanite 2CaO • 3B 2 3 • 5H 2 



Fremontite Na 2 0-Al 2 3 -P 2 5 -(H 2 0, 2HF) 



Vivianite 3FeO-P 2 Gv8H 2 



Pectolite Na 2 0-4CaO-6SiGvH 2 



Calamine 2ZnO-Si0 2 -H 2 



Chondrodite 4MgO-SiGvMg(F, 0H) 2 



Turquoise CuO-3Al 2 Gv2P 2 Gv9H 2 



Topaz 2A10F-Si0 2 



Celestite SrO-S0 3 



Prehnite 2CaO-Al 2 Gv3SiGvH 2 



Barite BaO-S0 3 



Anthophyllite MgO-Si0 2 



Sillimanite A1 2 3 - Si0 2 



Forsterite 2MgO-Si0 2 



Enstatite MgO ■ SiOj 



Euclase 2BeO-Al 2 Gv2SiGvH 2 



Triplite 3MnO-P 2 6 -MnF 2 



Spodumene Li 2 0-Al 2 Gv4Si0 2 



Diopside CaO-MgO-2Si0 2 



Olivine 2(Mg, Fe)0-Si0 2 



Triphylite Li 2 0-2(Fe, Mn)0-P 2 5 



Zoisite 4CaO-3Al 2 3 -6Si0 2 -H 2 



Strengite Fe 2 3 -P 2 5 -4H 3 



Diaspore A1 2 3 ■ H 2 



Staurolite 2FeO • 5 Al 2 O s • 4Si0 2 • H 2 



Chrysoberyl BeO • A1 2 3 



Azurite 3CuO-2C0 2 -H 2 



Scorodite Fe 2 3 • As 2 5 ■ 4H 2 



{continued) 



Index of refraction 



SMITHSONIAN PHYSICAL TABLES 



