186 BULLETIN 118, UNITED STATES NATIONAL MUSEUM. 



Euxeaite= complex mineral containing columbium, titanium, and yttrium, and other 



elements. 

 Eye agate=concentric rings of agate with a dark center; also thomsonite. 

 E vestone = thomsonite . 



F. 



Fairy stone = twinned crystal of staurolite, forming a cross. 



False amethyst=purple fluorite. 



False chrysolite=moldavite. 



False diamond = quartz crystal. 



False emerald=green fluorite. 



False hyacinth=garnet. 



False lapis=agate or jasper artificially colored blue. 



False lapis lazuli=lazulite. 



False ruby = red fluorite. 



False sapphire=blue fluorite. 



False topaz=yellow quartz; also yellow fluorite. 



Fancy=term applied to stones having value other than intrinsic value. 



Fancy agates=agates showing delicate markings and intricate patterns. 



Fancy stone=unusual stone. 



Fashoda garnet=dark brownish-red pyrope (garnet). 



Feldspar=group of minerals, including orthoclase, microcline, albite, oligoclase, 

 andesine, labradorite, aluminum and potassium, sodium, or calcium silicates. 



Feldspar sunstone=sunstone. 



Female sapphire=light-colored sapphire. 



Feminine=term applied to stones of a paler color than masculine ones. 



Fergusonite= black mineral composed chiefly of yttrium columbate. 



Figure - stone = agalmatolite . 



Fire marble = dark-brown shell marble with brilliant firelike internal reflections. 



Fire opal = red or yellowish-red opal. 



First bye = diamond with a faint greenish tint. 



First water =pure and colorless diamond. 



Fish-eye = moonstone . 



Fish-eye stone =apophyllite. 



Flash opal=opal in which the color shows as a single flash. 



Fleches d' amour =sagenite (quartz). 



Fleurus diamond = quartz crystal. 



Flint=compact silica, opaque, and of dull colors. 



Floating light=cymophane. 



Flos ferri=aragonite in shapes resembling coral. 



Flowers of iron=flos ferri (aragonite). 



Flower stone = beach pebbles (chalcedony) with flower patterns. 



Fluorspar = fluorite . 



Fluorite = calcium fluoride. 



Fool's gold=pyrite. 



Fortification agate=agate with parallel zigzag lines. 



Fossil coral=coral replaced by silica (beckite). 



Fossil pineapple=opal pseudomorph after glauberite, from New South Wales. 



Fossil turquoise = bone turquoise. 



Fowlerite= variety of rhodonite containing zinc. 



Franklinite= black iron, manganese, and zinc oxide. 



Frost stone = translucent gray chalcedony with pure-white patches or tufts, Like snow- 

 flakes, scattered through it, from the Mojave desert, California. 



Fuchsite=green muscovite (mica). 



