Lab Notes Gems & Gemology, Fall 2013, Vol. 49, No. 3

Purple Jadeite Rock

Figure 1. This 13.60 mm mottled purple bead consists primarily of jadeite and quartz. Photo by Robison McMurtry.
The Carlsbad laboratory recently took in a semi-translucent mottled purple bead for identification. Under microscopic examination, the material displayed an aggregate structure com­posed of fibrous lavender grains with a brownish white component (figure 1). Reddish orange minerals and small needle-like brown crystals were also observed. A spot RI reading of 1.55 was obtained on most of the stone, with a few places giving a reading of 1.66. The bead had a hydrostatic SG of 2.99 and was inert to both long- and short-wave UV radiation.

Basic gemological testing was inconclusive, but Raman spectroscopy performed on the various components of the stone confirmed the lavender and white portions were a mixture of jadeite and quartz, while the reddish orange portions were cinnabar. Additional spots on the scattered needle-like inclusions matched aegerine, a sodic-ferric clinopyroxene (figure 2). In addition to Raman testing, an infrared (FTIR) spectrum was collected to confirm the stone was not polymer-impregnated (E. Fritsch et al., “Identification of bleached and polymer-impregnated jadeite,” Fall 1992 G&G, pp. 176–187; Spring 1994 Lab Notes, p. 43).

Figure 2. Upon closer examination, the jadeite rock also contains reddish orange cinnabar and brown aegerine crystals. Photomicrograph by Nathan Renfro; magnified 30×.
Purple rock containing jadeite and quartz has been reported in the Bursa region of western Turkey (M. Hatipoǧlu et al., “Gem-quality Turkish purple jade: Geological and mineralogical characteristics,” Journal of African Earth Sciences, Vol. 63, 2012, pp. 48–61). To date, the composition of this material is unique to the area. It occurs as a metamorphic product in the contact zone between a large blueschist belt and a granodiorite stock. While neither mercury nor cinnabar (a mercury sulfide) is mentioned in the literature on purple jadeite rock, mercury mining in western Turkey has been reported (M. Yildiz and E.H. Bailey, “Mercury deposits in Turkey,” U.S. Geological Survey Bulletin 1456, 1978).

The presence of mercury deposits in the region makes it highly likely that cinnabar or other mercury-bearing minerals would occur in the purple jadeite rock, consistent with a Turkish origin, though the origin of this sample has not been confirmed. Because jadeite and aegerine are both sodic pyroxenes, their occurrence together is understandable.

Purplish jadeite rock is being used in the jewelry trade and fashioned into beads, cabochons, and carvings.

Tara Allen and Amy Cooper are staff gemologists at the GIA laboratory in Carlsbad, California.