In September 1998, emeralds were discovered at Regal Ridge (also known as the "Crown showing") in the Finlayson Lake area of southeastern Yukon Territory (61º17'N, 130º35'W). The deposit was found by geologists working for Expatriate Resources, who were exploring for base metals in the area along the Tintina fault. Preliminary reconnaissance of the deposit was encouraging, and in summer 2001 the first mechanized prospecting was performed by True North Gems Inc., Vancouver, Canada. True North has an option with Expatriate for 50% ownership of the property in exchange for a US$1.1 million work commitment over five years. This contributor, a consultant for True North, showed rough and cut emeralds from the exploration work to G&G editors at the 2002 Tucson gem show. Representatives of True North—Bernard Gaboury and Brad Wilson—also provided information for this report.

The Regal Ridge emerald occurrence encompasses a surface area of approximately 900 x 400 m, with a depth down to 100 m. The emeralds occur in sulfate-tourmaline zones in altered chlorite-mica schist adjacent to quartz veins, and rarely within the veins (see L. A. Groat et al., "Canadian emeralds: Geology, mineralogy, and origin of the Crown showing, southeastern Yukon," Canadian Mineralogist, manuscript accepted 2002). At least eight such veins, up to 1 m thick, have been identified. The best emeralds are a saturated bluish green with high clarity (see figure; 0.11 ct, photo by Brad Wilson); Groat et al. report average values of 3,208 ppm Cr and 171 ppm V from electron microprobe analyses of 25 samples. Most of the stones faceted so far are small (i.e., less than 0.25 ct); the largest faceted stone is 0.50 ct, and the largest cabochon weighs 2.08 ct. The small stone sizes are thought to result from the breakage of the near-surface material during seasonal freeze-thaw cycles in the arctic environment. Intact crystals of significant size are anticipated in the permafrost zone, below about 10 m depth.

Five faceted emeralds (0.09–C0.14 ct) from Regal Ridge were loaned to GNI by True North. Standard gemological properties were obtained by GIA's Elizabeth Quinn: R.I.—n_ω=1.587–1.591, n_ε=1.579–1.584; birefringences—0.007–0.008; S.G.—2.70–2.76; and inert to long- and short-wave UV radiation. Cr absorption lines were seen with a desk-model spectroscope. These properties are consistent with emeralds from other localities, although the R.I. values are relatively high (i.e., comparable to emeralds from Zimbabwe, Zambia, and Madagascar; see R. Webster, Gems, 5th ed., Butterworth-Heinemann, Oxford, England, 1994).

Microscopic examination of these samples by John I. Koivula of the GIA Gem Trade Laboratory in Carlsbad revealed minute black crystals (possibly chromite); slightly rounded, brassy yellow crystals (possibly pyrite); near-colorless crystals with the appearance of a carbonate; two- and three-phase inclusions (some with birefringent solid phases); and color and growth zoning that formed a partial hexagonal pattern when viewed parallel to the optic axis. Groat et al. identified the following mineral inclusions in their samples: calcite, chalcopyrite, molybdenite, phlogopite, pyrite, quartz, tourmaline, and zircon; also chromite, scheelite, and other minerals were identified within tiny cavities in their samples.

Regal Ridge is Canada's first potentially commercial emerald deposit. True North is continuing its evaluation program with surface and bulk samples in summer 2002.

William Rohtert
Hermosa Beach, California