In August 2003, an unusually dark blue beryl was discovered in Canada’s Yukon Territory by Bill Wengzynowski (Archer Cathro & Associates, Vancouver, British Columbia) and one of these contributors (LAG). Mr. Wengzynowski also is credited with the 1998 discovery of the Regal Ridge emerald deposit in the Yukon Territory, which is ~100 km east-southeast of the blue beryl occurrence. These efforts were financed by True North Gems Inc. of Vancouver. The new gem is noteworthy for its dark blue color and strong dichroism, and is being referred to as “True Blue” beryl.

One of the contributors (WRR) visited the True Blue property shortly after it was discovered. The beryl occurs in a swarm of closely spaced quartz-carbonate-tourmaline veins that cut a Mississippian-age (320 million years) fluorite-bearing syenite stock. The veins range from 0.5 to 20 cm thick, and locally comprise up to 30% of the rock overall. The vein zone measures 700 x 200 m in outcrop at the surface, and is exposed over an elevation range of 100 m. Within this area, more than 100 individual occurrences of the beryl have been found on the surface.

In September 2003, True North Gems Inc. hand collected 65 kg of samples from outcrop in the vein zone, which contained 57.9 grams of blue beryl. Individual crystals ranged up to 38 mm long and 11 mm in diameter. Five stones have been faceted thus far (see figure): two elongated emerald cuts (0.82 and 0.79 ct) and three round brilliants (0.06–0.11 ct). Prior to cutting, the pieces of rough were stabilized with Epo-Tek 301 epoxy. The stones were resin-impregnated again after preforming, and then once more, if needed, after faceting. The hue is maintained at exceptionally small sizes for aquamarine (e.g., in the 1 mm round brilliants). The main constraints on the size of the stones faceted to date are the abundant fractures present in the material gathered from the surface, and the typically small diameter of the crystals.

The five faceted samples were examined by one of us (EPQ) at GIA, and the following properties were obtained: color—dark grayish greenish blue, with strong dichroic colors of deep blue to violetish blue and pale greenish blue to near colorless; diaphaneity—semitransparent to translucent; R.I.—n_o=1.597–1.601, n_e=1.589–1.594; birefringence—0.008–0.009; S.G. of the two larger stones (measured hydrostatically)—2.78 and 2.79; Chelsea color filter reaction—none; fluorescence—inert to long- and short-wave UV radiation; and only general absorption to approximately 430 nm was observed with the desk-model spectroscope.

Microscopic examination revealed that all five samples were fairly heavily included, which significantly affected their transparency. Internal features included fractures, “fingerprints,” growth tubes, two-phase fluid-and-gas inclusions, transparent near-colorless quartz crystals (identified with Raman spectroscopy), and evidence of clarity enhancement; one stone had parallel planar clouds. One of the small stones had a surface-reaching inclusion that was surrounded by a thin layer of a dark brown submetallic material. With Raman analysis, the interior portion was identified as a carbonate (probably siderite) and the surrounding material was identified as pyrrhotite.

Seven fragments of the beryl, ranging from deep blue to medium blue, were chemically analyzed by electron microprobe by one of us (LAG) at the University of British Columbia. These samples showed relatively high iron contents, ranging from 1.54 to 5.81 wt.% FeO. The highest Fe content was found in the darkest blue sample, and surpasses the highest value for Fe in beryl that these contributors are aware of: 4.69 wt.% Fe oxides for a “bluish” beryl from Arizona (W. T. Schaller et al., “An unusual beryl from Arizona,” American Mineralogist, Vol. 47, 1962, pp. 672–699). The analyses also showed relatively high concentrations of Na and Mg, and traces of K, Ca, Sc, Ti, V, Cr, Mn, and Cs.

Polarized Vis-NIR absorption spectra of a deep blue, 0.68-mm-thick sample were recorded at the California Institute of Technology by GRR. The spectrum taken with light polarized parallel to the c-axis was dominated by a strong, wide band centered at about 850 nm. With light polarized perpendicular to the c-axis, this band was weak. The difference in absorption between these two orientations accounts for the strong dichroism shown by this beryl. The spectroscopic features indicate that iron is the chromophore responsible for the blue color.

There are two distinct varieties of blue beryl: aquamarine and Maxixe. In the material studied here, we observed that the lighter pleochroic color (pale greenish blue to near colorless) was carried on the ordinary ray (viewed with polarized light down the optic axis.) This is typical of aquamarine and not of the deep blue Maxixe beryl, where the colors are reversed and carried on opposite rays. Aquamarine sometimes has a spectrum that is visible (but not pronounced) with a desk-model spectroscope, comprising a line at 427 nm and occasionally a weak band at 456 nm, whereas Maxixe beryl typically has a series of six bands between 550 and 695 nm. None of the lines commonly seen in Maxixe beryl were found in the five faceted samples, but the general absorption to 430 nm may be due to the aquamarine 427 nm band (related to iron). The R.I.’s recorded for this material were a bit higher than those previously recorded for aquamarine (n_o = 1.572–1.590 and n_e = 1.567–1.583), whereas the S.G. values of the two samples tested fell within the reported range for aquamarine, 2.66–2.80 (R. Webster, Gems, Butterworth-Heinemann, Oxford, England, 1994, p. 124).

William  R. Rohtert (william.rohtert@gte.net)
Hermosa Beach, California

Elizabeth P. Quinn
GIA Gem Laboratory, Carlsbad

Lee A. Groat
University of British Columbia
Vancouver, British Columbia, Canada

George R. Rossman
California Institute of Technology
Pasadena, California