Hunt for gold leads junior to emeralds

In exploring for gold in the central Kivalliq region of Nunavut this field season, North Country Gold Corp. has found evidence of emerald in drill core at the Anuri prospect on its 300-kilometer- (186 miles) long Committee Bay Greenstone Belt Property.

The junior's Nunavut land package at Committee Bay consists of 222,623 hectares (550,101 acres) and has identified five distinct mineral development centers, including the Anuri-Raven prospect and the Three Bluffs gold deposit where the company has focused exploration in recent years.

Located 180 kilometers (112 miles) northeast of the Meadowbank Mine, Committee Bay is one of the largest remaining greenstone belts in Canada. The discovery of emerald on the property - only the fourth documented occurrence in Canada - brings to all three northern territories known discoveries of the rare gemstone. Discoveries of emerald also have been reported in northern British Columbia and northern Ontario.

Emeralds in Canada

Emeralds have been discovered at Ghost Lake near Dryden in northwestern Ontario, near Lened Creek in southwestern Northwest Territories, at Red Mountain near Stewart in northwestern British Columbia, and on the Tsa Da Glisza (formerly Regal Ridge) property in southeastern Yukon Territory.

Emerald is a rare variety of beryl (Be3Al2Si6O18), a rock-forming cyclosilicate mineral, generally occurring within granites and granitic pegmatites. Other varieties of beryl include aquamarine (blue), red beryl, goshenite (colorless), heliodor (yellow), and morganite (pink or peach). Of all varieties of beryl, emerald is the most prized, and can be worth more than US$100,000 per carat.

Beryl is a relatively rare mineral because there is very little beryllium in the earth's crust. It is found in small amounts in granites and pegmatites, according noted emeralds expert, Lee A. Groat, Ph.D.

In addition to the presence of beryllium, emeralds require a sufficient amount of chromium or vanadium during crystallization. These two elements are nearly as rare as beryllium in the earth's crust and even rarer in granites. In addition, researchers say the three elements generally come from different magma sources. Chromium and vanadium are normally found in mafic or ultramafic rocks and their metamorphic equivalents, that is, rocks very low in silica, while beryllium generally is found in rock known as "evolved," meaning very rich in silica, such as granites and pegmatites.

The classic model of emerald formation is exactly those conditions under which evolved rocks (granites and pegmatites) interact with mafic or ultramafic rocks, according to Groat and others.

The necessary conditions for emerald formation are, however, extremely complex.

The "interaction" between the two source reservoirs must occur through hydrothermal fluids.

Hydrothermal fluids are hot water that can carry dissolved beryllium, chromium or vanadium from their source to the location of emerald crystallization.

These fluids must generally be present when the granites, pegmatites, or mafic or ultramafic rocks are deposited, or else when they are metamorphosed.

The fluids travel through naturally occurring pores in the rock or along flaws or cracks.

As they do so, they "wash out" the beryllium, chromium or vanadium contained in the rock and carries it elsewhere.

When these elements all come together, the chances of emerald formation is increased.

Geologists say the green color of emerald reflects the trace amounts of chromium and/or vanadium replacing aluminum in its crystal structure; the color may be diminished by the presence of iron which can add a greyish tint.

There is debate over the difference between emerald and green beryl; however, a definition that appears to be attaining broad acceptance among scientists is that emeralds are yellowish green, green or bluish green, natural or synthetic beryls, which reveal distinct chromium and/or vanadium absorption bands in the red and blue-violet ranges of their absorption spectra.

There are many classification schemes for emerald deposits. Researchers in 2002 divided emerald deposits into the following categories: pegmatites without schist, pegmatite and greisen with schist, schists without pegmatites, and black shales with veins and breccias. Beryl occurrences in Canada are mostly associated with either Archean pegmatites in the Canadian Shield or Mesozoic/Cenozoic granitoids in the Cordilleran.

Emeralds in Ontario

Canada's first emerald discovery, known as the Taylor 2 pegmatite after J.G. Taylor, was reported near Dryden in northwestern Ontario in 1940.

The Taylor 2 pegmatite belongs to the Mavis Lake Pegmatite Group, which is southeast of the S-type peraluminous Ghost Lake batholith.

Porcellaneous white to pale green beryl crystals, up to several centimeters long and 5 centimeters wide, are found within a 3.5-kilometer (2.2 miles) by 1.5 km (0.93 mile) area.

The beryl is concentrated in two pegmatite dykes situated 340 meters south of the Ghost Lake batholith, but only the Taylor 2 pegmatite contains emerald.

Most of the beryl and emerald occurs within a "zone of mixing" between the southern and central limbs of the pegmatite.

The "zone of mixing" consists of relict K-feldspar crystals from the pegmatite in a matrix of albite, biotite, and tourmaline.

Scientists have compared the geologic setting at Ghost Lake to that of the Somerset Hill mine in the Gravelotte district in South Africa.

This occurrence has also been suggested to be of metamorphic origin.

Emeralds in Northwest Territories

Whitehorse-based prospector Ron Berdahl discovered vanadium-rich emeralds near the Lened tungsten showing in the westernmost Northwest Territories, adjacent to the Yukon border in the late 1970s.

The transparent pale-green emerald crystals were found 55 kilometers (34 miles) northwest of the town of Tungsten in the Logan Mountains.

The occurrence is located on the eastern margin of the Selwyn Basin, which consists of deformed and weakly metamorphosed Neoproterozoic to Devonian-Mississippian sedimentary rocks interpreted as a continental terrace wedge along the western margin of the North American Craton.

The basin is separated from the craton by a major tectonic flexure known as the Redstone arch.

Emerald at the Lened emerald showing is hosted by quartz-carbonate veins developed within a skarn assemblage.

The veins (2-30 centimeters wide) extend perpendicularly from the thrust fault across the skarn and pinch out in overlying rhythmically bedded limestone.

The black shale footwall unit is devoid of emerald mineralization.

The emerald is intergrown with quartz and calcite adjacent to the wallrock and concentrations are highest near vein-fault intersections.

The veins are surrounded by a 5- to 10-cm-wide alteration zone that consists of calcite, dolomite, diopside, hedenbergite, vesuvianite, and base-metal sulfides.

Emerald crystals from Lened are typically euhedral, up to 3 centimeters in length and 3 millimeters in diameter, although the longest crystals tend to be quite narrow.

Most of the crystals are pale green to yellow, but some are dark grassy-green.

Chemical analyses indicate that the emerald is richer in vanadium (up to 0.5 wt.

percent V2O3) than in chromium.

The property is currently owned by Liberty Mineral Exploration Inc.

Emeralds in B.C. and the Yukon

Crystals of deep-green beryl were discovered in 1989 at Red Mountain, near Stewart on the central coast of British Columbia. The beryl occurs as small opaque crystals having numerous fractures in narrow quartz-calcite-pyrite veins cutting volcaniclastic rocks adjacent to a quartz-monzonite intrusion. Electron microprobe analyses show 1,612 ppm vanadium and 1.04 wt. percent ferrous oxide (average of six analyses), and no detectable chromium.

After further investigation in 1997, geologists reported poorly formed vanadian emerald associated with the Red Mountain porphyry deposit near Stewart, but information is minimal.

In 1998, Bill Wengzynowski discovered emerald at Tsa Da Glisza (which means "green stones" in the indigenous language of the Kaska First Nation) in the southeastern Yukon Territory near the town of Ross River.

At Tsa Da Glisza, the emeralds occur in quartz and tourmaline veins that cut across metamorphosed volcanic rocks.

The mineral occurrence is associated green to green-blue to "emerald green" beryl crystals up to 4 centimeters in length that occur in 12 mineralized zones within a 900-meter by 900-meter area.

Chromium (average 3,208 ppm) is the predominant chromophore.

Some of the smaller crystals, and sections of larger crystals, are gem-quality, and a number of small gems (up to 2.4 carats) have been fashioned from Tsa da Glisza samples.

The property currently belongs to True North Gems Inc.

Emeralds in Nunavut

At the Anuri prospect in Nunavut, emerald crystals were initially noted by a North Country Gold geologist when investigating highly elevated beryllium values contained within potassic altered Prince Albert Group komatiites from drill core that the explorer was evaluating as a gold target.

Preliminary evaluation of the crystals utilizing X-ray diffraction and electron microprobe confirmed that the crystals are beryl and that the dominant chromophore is chromium with essentially no vanadium.

The occurrence of the gemstone will be the focus of a research project at the University of British Columbia under the direction of Groat, an associate professor in UBC's Department of Earth and Ocean Sciences.

UBC researchers will investigate the origin of the Anuri emerald mineralization and will form the basis of an exploration strategy to fully assess the potential for discovery of economic emerald mineralization in the Committee Bay greenstone belt.

"The discovery of emeralds at Anuri is only the fourth documented occurrence in Canada," said North Country Gold President and CEO John Williamson in announcing the Nunavut find Oct. 16. "North Country is pleased to have one of the world's foremost emerald experts, Professor Lee Groat, initiate research on the emerald mineralization in the Committee Bay Greenstone Belt, and we are intrigued by the implications of further exploration and the potential for more discoveries of economic deposits."

"The discovery of emerald mineralization at North Country Gold's Anuri property is exciting for a number of reasons," said Groat. "Emerald is extremely rare because it requires unusual geologic and geochemical conditions to form, and evaluating these conditions will provide important clues to the genesis of the Anuri prospect as a whole. We, at UBC, are excited to be working with North Country Gold on characterizing the world's most recently discovered emerald occurrence."

The Anuri occurrence is highly prospective for gold-silver mineralization and is characterized by a 0.5-kilometer- (0.31 mile) wide by 1.5-kilometer- (0.93 mile) long zone of intensely altered and sulphidized mafic and ultramafic volcanic float boulders.

Sampling of this boulder train has produced high-grade gold and silver values up to 291.2 grams per metric ton gold and 1,769.5 g/t silver, 20.68 g/t gold and 333.0 g/t silver, and 14.44 g/t gold and 394.0 g/t silver.

Initial drill testing intersected gold and silver mineralization, with elevated copper, bismuth, lead, zinc and cadmium values with hole 06AR007B intersecting 3.75 g/t gold, 63.7 g/t silver, 0.75 percent copper and 158.2 parts-per-million bismuth over 10.21 meters.

Strong to intense potassic alteration along with silicification and sulphidation was encountered in the mafic and ultramafic stratigraphy.

The distribution of Prince Albert Group komatiites in the Committee Bay greenstone belt is extensive, forming a 25-kilometer (16 miles) by 10 kilometer (six miles) belt in the southwest portion of the area. Potassic alteration has been identified throughout the area in association with broad zones of shearing and emplacement of late granitoid intrusions, which has implications for the widespread occurrence of emerald mineralization in the area.

The results of the research into the genesis of the emeralds will provide key information to develop an exploration model to fully evaluate the potential of the new discovery in the Committee Bay Greenstone Belt.

Targeting gold at Three Bluffs deposit

Until now North Country Gold has focused almost exclusively on exploration of the Three Bluffs deposit, a structurally controlled lode gold system hosted within oxide facies iron formation and greywackes, at Committee Bay. The deposit comprises a current NI 43-101-compliant resource of 4.30 million metric tons averaging 4.90 g/t gold for 678,000 ounces gold (indicated) and 4.53 million metric tons averaging 5.69 g/t gold for 829,000 ounces gold (inferred). The deposit is hosted within a roughly 50-meter wide, steeply dipping banded iron formation unit which can be traced for more than 10 kilometers (six miles).

North Country believes the Three Bluffs deposit is amenable to development as an open-pit mine with underground potential and is working to define a 3-million-ounce gold resource. To date, the deposit has been drill tested at shallow levels along a strike length of 4.1 kilometers (2.6 miles). It has been most extensively drilled over the eastern 1.3 kilometers of the trend where drilling up to 2011 reached depths of 300 meters below surface.

Last spring, North Country completed 7,005 meters of diamond core drilling in 12 holes to depth in the eastern part of the deposit, which extended the mineralized envelope to depths of 500 meters below surface with mineralization remaining strong and open to depth. This new drilling is expected to result in an increase in the underground inferred resource of the deposit.

Geological modeling of the Three Bluffs gold system has identified several controls on high-grade mineralization including steep east plunging shoots and shallow east plunging fold hinges within the iron formation.

In 2010, North Country Gold completed a Quantec Titan 24 geophysical survey over the Three Bluffs project, which indicated that known gold zones at shallow to intermediate depths display an excellent correlation with DC-resistivity lows.

These resistivity lows extend to least 500 meters depth over much of the surveyed area, and the correlation of gold mineralization with the resistivity lows to depth has been confirmed by high grade intersections to these depths within the 2012 drill program.