212 BULLETIN 118, UNITED STATES NATIONAL MUSEUM. 



V. Color yellow — Continued. 



A. Transparent or nearly so — Continued. 



(c) Hardness less than 7; scratched by quartz. 



1. Sp. gr. fairly high, 3.4; pleochroism distinct Titanite, sphene. 



2. Sp. gr. mostly less than 3; isotropic Glass (artificial). 



3. Sp. gr. very low, 1.1 Amber. 



(The rarely used yellow forms of apatite, chrysolite, fluorite, microlite, 

 sphalerite, spodumene, vesuvianite, and willemite belong here.) 



B. Opaque or nearly so. 



(a) Hardness greater than 6; scratch microcline. 



1. Sp. gr. medium, 2.6 (in part artificially colored) Chalcedony. 



2. Like preceding, but more opaque Chalcedony, jasper. 



3. Luster silky Quartz after crocidolite. 



(6) Hardness less than 6; do not scratch microcline. 



1. Sp. gr. mostly below 3; luster glassy Glass (artificial). 



(The rare yellow varieties of serpentine and smithsonite, and the little 

 used mineral cancrinite belong here.) 



VI. Color brown (including orange-color). 



A. Transparent or nearly so. 



(a) Hardness 9 or greater; not scratched by corundum. 



(The rare brown-colored diamond belongs here.) 



(b) Hardness 8 to 7; scratched by corundum but not by quartz. 



1. Sp. gr. high, 4.5; double refraction strong, very brilliant Zircon. 



2. Sp. gr. high, 4.1; isotropic . .Garnet, essonite, spessartite. 



3. Sp. gr. fairly high, 3 Tourmaline. 



4. Sp. gr. medium, 2.7 Quartz, smoky. 



(The rarely used mineral staurolite, and the rare brown-colored varieties 

 of andalusite, chrysoberyl, spinel, and topaz belong here.) 



(c) Hardness less than 7; scratched by quartz. 



1. Sp. gr. fairly high, 3.4; pleochroism distinct Titanite. 



2. Sp. gr. medium, mostly less than 3; isotropic Glass (artificial). 



3. Sp. gr. very low, 1.1 ■ Amber. 



(The rarely used minerals axinite, epidote, fluorite, chondrodite, 

 sphalerite, staurolite, and vesuvianite belong here.) 



B. Opaque or nearly so. 



(a) Hardness greater than 6; scratch microcline. 



1. Sp. gr. high, 3.7; color deep brown Staurolite. 



2. Sp. gr. medium, 2.6; in part artificially colored Chalcedony. 



3. Same, banded Chalcedony, agate. 



4. Same, but more opaque Chalcedony, jasper. 



5. Same, but luster highly silky Quartz after crocidolite. 



(b) Hardness less than 6; do not scratch microcline. 



1. Sp. gr. medium, 2.6 Obsidian. 



2. Sp. gr. mostly less than 3 Glass (artificial). 



(Some rarely-used varieties of feldspar and altered staurolite belong here.) 



VII. Color red or pink. 



A. Transparent or nearly so. 



(a) Hardness 9 or greater; not scratched by corundum. 



1. Does not scratch corundum surface Corundum, ruby. 



(The rare pink colored-diamond belongs here; it scratches corundum.) 



