CATALOGUE OF GEMS AND PRECIOUS STONES. 53 



FELDSPAR, variety PERTHITE. 

 CANADA (PERTH, ONTARIO). 



Cabochon, elliptical girdle; brown; 100.47 carats; 45 by 35 by 10 mm. Isaac 

 Lea collection No. 386 



Cabochon, rectangular girdle; brown with white veins; 17.85 carats; 33 by 13 

 by 5 mm No. 385 



FELDSPAR, variety SUNSTONE. 



NORWAY. 



Cabochon, circular girdle; red-brown; two pieces; 20 and 18.5 carats; 23 by 6 



. and 23 by 5.5 mm No. 1196 



Cabochon, rectangular girdle; red-brown; 7.93 carats; 32 by 9 by 3 mm No. 1199 



Four cabochons, one double cabochon, elliptical girdle; red-brown; 7.6 



carats to 2.4 carats; 17 by 13 by 5 to 9 by 8 by 4 mm. Isaac Lea collection . . No. 1197 

 Double cabochon, elliptical girdle; red-brown; 5.26 carats; 14 by 11 by 5 mm. 



Isaac Lea collection No. 1198 



Three cabochons, two elliptical, one square girdle; dark gray, blue internal 



color; 11.08, 5.06, and 3.5 carats; 20 by 12 by 7, 14 by 10 by 4.5. and 11 by 



4 mm No. 1200 



UNITED STATES. 



Pennsylvania. 

 Media, Delaware County: 



Cabochon, elliptical girdle; two stones, one red -gray, one light gray; 



56.37 and 19.67 carats; 43 by 32 by 6 mm. and 27 by 19 by 5.5 mm No. 1202 



Tabular cabochon, rectangular girdle; gray with pale brown streaks; 



6.77 carats; 19 by 11 by 3 mm. Gift of Dr. R. H. Lamborn No. 1201 



FLUORITE. 



Synonym. — Fluor-spar. 



Composition. — Calcium difluoride, CaF 2 . 



Crystallization. — Isometric. 



CoZor.— Colorless when pure, but usually showing disperse colors 

 owing to the presence of submicroscopic particles of indeterminate 

 nature; may be a beautiful yellow, green, blue, violet, or pink. 



Luster. — Vitreous; transparent to translucent. 



Hardness. — 4; too soft for ordinary use as a precious stone, but 

 can be used in ornaments, etc. 



Specific gravity. — 3.18 ±0.05. 



Optical properties. — Refractive index, 1.434; optically isotropic; 

 may show T fluorescence or different colors when viewed by reflected 

 and transmitted light, but never pleochroism. 



The mineral is distinguished by its softness, by its lack of double 

 refraction, and its easy and perfect octahedral cleavage. It occurs 

 in veins in many kinds of rocks, including the pegmatites. 



