The Periodic Spiral assigns the color purple (red violet) to nitrogen, yttrium, technetium, silver, and antimony. Minasgeraisite, a rare yttrium beryllium silicate, has an attractive color, pale lavender to purple. Yttrium fluorite is a light purple color showing a fine translucency. Purple YAG (yttrium aluminum garnet) is marketed as Purple Coranite. Silver tarnishes in air to a variegated purple-black color. The unusual and colorful mineral kermesite, antimony oxysulfide (Sb2OS2) is alternately called purple blende.