Amethyst from Four Peaks, Arizona
NOTES & NEW TECHNIQUES AMETHYST FROM FOUR PEAKS, ARIZONA Jack Lowell and John I. Koivula and shapes (Lurie, 1998, 1999; Johnson and For more than a century, the Four Peaks mine in Koivula, 1998). Currently, it is owned and operat- Maricopa County, Arizona, has produced gem- ed by Four Peaks Mining Co. LLC of Ocean quality amethyst from crystal-lined or crystal-filled Grove, New Jersey. The deposit is again producing cavities and fractures in a brecciated quartzite host good-quality amethyst, with some of the cut rock. Crystals from the deposit exhibit a range of stones exceeding 20 ct. purple colors, uneven color zoning, and variable This article provides a brief description of the transparency, which present challenges for obtain- geologic occurrence of amethyst at the deposit and ing a steady supply of material suitable for faceting. summarizes the gemological properties of this Faceted material may display fluid inclusions and material. Although previous descriptions of the tiny reddish brown hematite flakes, growth zoning, deposit and local geology can be found in and Brazil-law twinning, all of which provide visual clues to separating the Four Peaks material from Sinkankas (1957, 1976, pp. 373–374), Lowell and synthetic amethyst. Recovery of amethyst at this Rybicki (1976), Estrada (1987), Chronic (1989, pp. deposit continues at this time on a limited basis. 174–175), and Lieber (1994, p. 122), this article pro- vides the first gemological characterization of Four Peaks amethyst. he most important commercial source of gem- quality amethyst in the United States is the LOCATION AND ACCESS T Four Peaks mine in Maricopa County, The Four Peaks mine is named for the mountain area Arizona (figure 1).
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