214 BULLETIN 118, UNITED STATES NATIONAL MUSEUM. 



Possessing internal colors — Continued. 

 B. Opaque or nearly so. 

 (a) Hardness greater than 6; scratch microcline. 



1. (Some asteria corundum is practically opaque; see A. a 1.) 



Corundum, asteria. 



2. Int. refl. silky, forming broad band; color brown-yellow... Quartz, tiger-eye. 



3. Int. refl. silky, forming broad band; color gray, green, etc. .Quartz, cat's-eye. 



4. Int. refl. spangled; color various Quartz, aventurine. 



(6) Hardness 6 or less; do not scratch microline. 



1. Sp. gr. 3.4; int. refl. bronzy; color dark brown. 



Hypersthene (including bronzite). 



2. Sp. gr. 2.7; shows pearly luster and delicate color-play Calcite, pearl. 



3. Sp. gr. 2.7; color gray; int. refl. blue, green, red, etc.. Feldspar, labradorite. 



4. Sp. gr. 2.7; color gray; int. refl. red, spangled Feldspar, sunstone . 



5. Sp. gr. 2.5; color dull green; int. refl. silky, gray Serpentine, satelite. 



6. Sp. gr. 2.3; very soft, color white: int. refl. strongly silky. 



Gypsum, satin-spar. 



