Feature Gems & Gemology, Fall 2004, Volume 40, No. 3

Amethyst from Four Peaks, Arizona

For more than a century, the Four Peaks mine in Maricopa County, Arizona, has produced gem-quality amethyst from crystal-lined or crystal-filled cavities and fractures in a brecciated quartzite host rock. Crystals from the deposit exhibit a range of purple colors, uneven color zoning, and variable transparency, which present challenges for obtaining a steady supply of material suitable for faceting. Faceted material may display fluid inclusions and tiny reddish brown hematite flakes, growth zoning, and Brazil-law twinning, all of which provide visual clues to separating the Four Peaks material from synthetic amethyst. Recovery of amethyst at this deposit continues at this time on a limited basis.