Micro-World Gems & Gemology, Spring 2019, Vol. 55, No. 1

Native Copper Inclusions in Indonesian Purple Chalcedony

Native copper inclusions in purple chalcedony.
This purple chalcedony from Indonesia contained interesting inclusions of native copper. Photomicrograph by Nathan Renfro; field of view 5.74 mm.

As a gem material, chalcedony can contain an array of interesting structures and mineral inclusions. This was particularly evident in one example recently examined by the authors. Purchased by author SC from gemstone dealer John Garsow (John E. Garsow Gems & Minerals, Murrieta, California), this vibrant purple chalcedony reportedly from Indonesia contained several small clusters of what appeared to be native copper (see above). This suspicion was confirmed by energy-dispersive X-ray fluorescence (EDXRF) testing. While the origin of the purple color is not clear, it certainly does not appear to be related to copper. In purple areas that were devoid of copper inclusions, no copper was detected by EDXRF. We did detect iron, which may be related to the purple color.

While native copper inclusions have been previously reported in chalcedony (B.M. Laurs and N.D. Renfro, “Chrysocolla chalcedony with native copper inclusions,” Journal of Gemmology, Vol. 36, No. 2, 2018, p. 92), this is the first time the authors have examined purple chalcedony from Indonesia with native copper inclusions.

Nathan Renfro is manager of colored stones identification at GIA in Carlsbad, California. Stephen Challener is an independent gemologist in Raleigh, North Carolina.