522 



TABLE 543.— INDEX OF REFRACTION OF SELECTED MONOREFRINGENT 

 OR ISOTROPIC MINERALS 



The values are for the sodium D line unless otherwise stated and are arranged in the 

 order of increasing indices. Selected by Edgar T. Wherry from a private compilation of 

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



Index of 



refraction 



Mineral Formula X = 0.589/t 



Villiaumite NaF 1.328 



Cryolithionite 3NaF-3LiF-2AlF, 1.339 



Opal :■ SiGvnH,0 1.406 



Fluorite CaF, 1.434 



Alum K 2 -A1.0i-4SOi-24H,0 1.456 



Sodalite 3Na 2 0-3Al J Gv6SiGv2NaCl 1.483 



Cristobalite SiO, 1.486 



Analcite Na 3 0-AUGv4SiGv2H 2 1.487 



Sylvite KC1 1.490 



Noselite 5Na 2 0-3Al 2 3 -6Si0 2 -2S0 3 1.495 



Hauynite Like preceding + CaO 1.496 



Lazurite 4Na 2 0-3Al 2 Gv6SiGvNa 2 S„ 1.500± 



Leucite K 2 OAl 2 Gv4Si0 2 1.509 



Pollucite 2Cs 2 0-2Al 2 Gv9SiGvH 2 1.525 



Halite NaCl 1.544 



Bauxite Al a GvnH 2 1.570± 



Pharmacosiderite 3Fe 2 C>3 • 2As 2 6 • 3K 2 • 5H 2 1 .676 



Spinel MgO-Al 3 3 1.720=t 



Berzeliite 3(Ca, Mg, Mn)0-As 2 0, 1.727 



Periclasite MgO 1.736 



Grossularite 3CaO-Al 2 Gv3SiG* 2 1.736 



Helvite 3(Mn, Fe)0-3BeO-3SiGvMnS 1.739 



Pyrope 3MgO-Al 3 3 -3SiO, 1.745 



Arsenolite As 2 Os 1.754 



Hessonite 3CaO- (Al, Fe) 2 3 -3Si0 3 1.763 



Pleonaste (Mg, Fe)0-Al 2 3 1.770± 



Almandite 3FeO-Al 2 3 -3Si0 2 1.778 



Hercynite FeO- A1 2 3 1.800± 



Gahnite ZnO-Al 2 3 1.805± 



Spessartite 3MnO- Al 2 3 -3SiO, 1.811 



Lime CaO 1.838 



Uvarovite 3CaO-Cr 2 3 -3Si0 3 1.838 



Andradite 3CaO-Fe 2 3 -3Si0 2 1857 



Microlite 6CaO-3Ta 2 O s -NbOF 3 1.925 



Nantokite CuCl 1.930 



Pyrochlore Contains CaO, Ce 2 3 , Ti0 2 , etc. 1.960 



Schorlomite 3CaO-(Fe, Ti) 3 3 -3(Si, Ti)O a 1.980— 



Percylite PbO-CuCl 2 -H,0 2.050 



Picotite (Mg, Fe)0-(A1, Cr) 2 3 2.050± 



Eulytite 2Bi 2 8 -3Si0 2 2.050 



Cerargyrite AgCl 2.061 



Mosesite Contains Hg, NH«, CI, etc. 2.065 



Chromite FeO-Cr 2 3 2.070 



Senarmontite Sb 2 3 2.087 



Embolite Ag(Br, CI) 2.150± 



Manganosite MnO 2.160 



Bunsenite NiO 2.18 * 



Lewisite 5CaO-2Ti0 2 -3Sb 2 0., 2.200 



Miersite CuL4AgI 2.200 



Bromyrite AgBr 2.253 



Dysanalite Contains CaO, FeO, Ti0 2 , etc. 2.330 



Marshite Cul 2.346 



Franklinite (Zn, Fe, Mn)0-(Fe, Mn) 2 3 2.360* 



Sphalerite (Zn, Fe)S 2.370 



Perovskite CaO-TiO, 2.380 



Diamond C 2.419 



{continued) 



SMITHSONIAN PHYSICAL TABLES 



