Pink topaz from the Thomas Range, Juab County, Utah

The Thomas Range is world-famous for its production of topaz Al2SiO4(F,OH)2, occurring in lithophysal cavities in rhyolite. Topaz Valley, at the southern end of the range, is perhaps the single most famous locality. While fine-quality, sherry-orange crystals to 5 cm or more in length occur at various localities, pale to medium pink crystals were first reported from the Thomas Range in 1934. The cause of the unusual coloration, unknown for 60 years, is now believed to be substitution of Mn3+ ?? Fe3+ for Al3+. -Authors