Canadian Mining Journal

Feature

Canadian emeralds

According to his field notes, it was a rainy afternoon in August 1998 when Bill Wengzynowski, then a geologist exploring for base metals in the Finlayson district of the Yukon Territory, spotted something green. Thinking at first that it might be...


According to his field notes, it was a rainy afternoon in August 1998 when Bill Wengzynowski, then a geologist exploring for base metals in the Finlayson district of the Yukon Territory, spotted something green. Thinking at first that it might be an outcropping of the copper mineral, malachite, he took a closer look. As it turned out, it wasn’t copper, but something more rare, and potentially far more valuable: emerald.

Five years later, Vancouver-based True North Gems Inc., now the owner of Regal Ridge where the find was made, is hoping to develop Canada’s first commercial emerald mine at the property, located high in the rugged Pelly Mountains, 230 km northeast of Whitehorse.

The company completed a bulk surface-sampling program last year and then moved into an underground program in 2003. By October, their Cdn$2.1-million exploration program had uncovered three new emerald zones bringing the total to 13, and additional trenching and mapping had doubled the size of the total mineralized area. From Wengzynowski’s observation of the initial outcropping, the zone has grown to encompass an area measuring 1,500 m in length, 500 m in width and exposed over 200 m of vertical section. Diamond drilling and excavation work on the southwest zone has also confirmed the continuity of emerald mineralization underground.

By the end of 2002 True North was recovering emeralds over a wide area of the surface. Although the stones were consistently of a good colour and high quality, most were small, possibly the result of frost shattering. Emeralds above the permafrost level have been subjected to harsh arctic weather conditions for tens of thousands of years. Their crystal structure cannot withstand the extreme conditions and they fracture along natural cleavage planes. Although there is a market for small stones, called “melee” in the trade, they sell for a fraction of the value of the larger centre stones usually seen in rings or pendants. If that’s all the deposit can produce, it’s unlikely to be commercially viable.

True North was anxious to get underground as soon as possible to determine if larger emeralds existed below the frost zone. Much will therefore hinge on the results of 210 kg of highly concentrated emerald material recovered from recent activities and now at True North Gems’ laboratory in Vancouver. Once the concentrated emerald material has been classified and graded, test parcels of emerald rough will be forwarded to a number of cutting facilities in Canada and internationally for evaluation and cutting. An assessment of the performance of various cutting facilities will determine where the bulk of the 2003 gem, near-gem and non-gem material will end up being sent for finishing. True North was hoping to have representative parcels ready for tendered auction in late January 2004. The sale of Canada’s first emeralds will be the definitive test of the finished products’ values. According to True North, in a best-case scenario Yukon emeralds could start appearing in jewellery stores by late 2004.

History of emeralds

Some sources say the name “emerald” originates from a Persian word meaning “green gem”; others believe it has its roots in the Latin word for green, “smaragdus”. But beryl, a beryllium aluminum silicate (Be3Al2(SiO3)6), in its pure form is colourless. It is only when traces of chromium (or vanadium) replace aluminum in the crystal structure that it takes on its characteristic green colour.

Other impurities create different colours. Gemstone varieties of beryl include aquamarine (blue), morganite (pink), heliodor (greenish-yellow) and goshenite (colourless). But it is the deep, brilliant green of emerald that makes it one of the most sought-after gems in the world.

According to the Yukon Geological Survey, the first discovery of emerald in the Canadian north was actually made in 1997 when prospector Ronald Berdahl found green beryl stones near the Lened tungsten skarn deposit 50 km north of the Cantung mine in the Selwyn Mountains in the westernmost Northwest Territories. But the emeralds were found to be coloured by vanadium and were too pale and small to be considered of economic importance.

It is the chromium-enriched emeralds that are the most highly prized. They are rare because two of the elements essential for their creation, beryllium and chromium, are essentially incompatible geochemically in the Earth’s crust. The intense emerald green colour results from a phenomenon known as chromium fluorescence–the stones emit green light as well as reflect it.

Emerald is an ancient gemstone, making an appearance in historical records that date back over 4,000 years but, until the 16th century, Egypt was their only known source. Located along the country’s Red Sea coast on the slopes of the Sikait and Zubara Mountains, ruins of quarries, which came to be known as “Cleopatra’s mines”, are still visible today. Although those mines were exhausted long ago, for centuries after, emeralds continued to appear in the Western world.

Their origin was to remain a mystery until Spanish Conquistadors landed in the South American country known today as Columbia.

In the late 1990s, emeralds recovered from the shipwreck Nuestra Seora de Atocha played a critical role in determining the origins for many of the world’s renowned emerald jewels. The Atocha was a Spanish treasure ship that sank in 1622, just two days after leaving port. Down with the ship went a fortune in silver and gold bars, personal jewellery, hundreds of thousands of treasure coins–and emeralds from the Colombian mines. The wreck was discovered off the Florida Keys in 1985 and almost 6,000 uncut, ‘raw’ Colombian gems were recovered from the sunken treasure as well as stones that were already cut, polished, and mounted into gold settings.

A group of French and Colombian scientists had recently determined that levels of oxygen isotopes within emerald crystals were accurate source-point indicators, often linking a gem to an individual mine. In bombarding the emerald with a cesium ion beam, they were able to collect and analyze the dislodged oxygen ions, assigning them unique and specific values. Utilizing Atocha emeralds as test subjects, they confirmed the stones’ Colombian origins.

The researchers then examined emeralds from collections around the world, re-evaluating their supposed origins. Their research changed a long-accepted theory that all gem quality emeralds in the ancient world came from either from Egypt or Austria. Although some were found to have originated in Pakistan and Afghanistan, the big surprise was that most emeralds believed ‘ancient’, were actually mined in Colombia, and shipped to the Old World by the Spanish fleets during the 16th and 17th centuries.

Like most gemstones (aside from diamond), little is known about the genesis of emerald deposits or the physio-chemical conditions under which they form. The possibility of emerald occurrences in the Yukon was first suggested by Lori Walton (prior to their discovery) in her publication entitled “Exploration Criteria for Gemstone Deposits and their Application to Yukon Geology” (Open File 1996-2 (G) from the Yukon Geological Survey). According to Walton, who studied the geology of 40 emerald deposits world-wide, all are associated with pegmatitic/granitic rocks interacting with ultramafic rocks except for one–the unique Colombian emeralds formed in bituminous black shales and sedimentary rocks. Emerald deposits related to pegmatites or granites are further classified as those in recent suture zones (Type 2a) or those in ancient suture zones (Type 2b). The Yukon discoveries are said to be Type 2a, somewhat similar to the Kafubu deposit in Zambia; roughly half the volume and a quarter of the value of the global emerald production is derived from this class.

Emeralds are found concentrated in narrow bands a few metres wide over varying lengths and occur in pods. In many respects emerald mineralization can be likened to a high-grade gold vein. Mining is basic–dig up the emerald-bearing rock, break it apart and separate o
ut the stones. Modern techniques such as magnetic separation technology and dense media separation could replace the labour-intensive hand-sorting methods used in most emerald mines.

Mining and processing may turn out to be relatively straightforward but developing the reserves in a gemstone deposit is a challenge. There are no accepted protocols for the projection of drill results for coloured gemstone deposits. True North is working with researchers at the University of British Columbia to develop a methodology, hoping the results from the diamond drilling and underground work will supply the data necessary to create geological models for predicting emerald occurrences. In the meantime the only tangible way is to count gemstone recoveries from their underground adits and surface trenches.

Today, annual global emerald sales account for a Cdn$2.2-billion industry and Columbia remains the champion in terms of both quality and quantity, providing around 40% of the world’s output and accounting for 75% by value of all emerald sold. Emeralds of varying (but generally inferior) colour, clarity, and quality are also mined in Brazil, Pakistan, Afghanistan, Madagascar, Nigeria, Russia, Zambia, and Zimbabwe.

Unlike diamonds, emeralds have no industrial use, but a gem-quality stone can be more valuable than an equivalent diamond. Quality stones command US$1,500 to US$7,000 per carat but higher prices are not unheard of. The highest price paid for a single emerald is reportedly 1,320,488 (around US$2 million), for a 19.77-carat emerald and diamond ring made by Cartier in 1958, and sold at Sotherby’s, Geneva, on April 2, 1987.

But again, unlike the diamond industry, there is no established pipeline to get emeralds from mine to market. Traditionally, gem quality stones pass through an intricate and close-knit network, moving along an unregulated path from small mines to international cutters, dealers and finally to customers. Emeralds are often implicated as the currency for illegal activity, especially in countries like Colombia and Afghanistan.

True North’s plan

The True North plan is based on capitalizing on the Canadian location to market its production, targeting the North American jewellery market in general. The company hopes to become a wholesaler of cut stones marketing them as a Canadian product, using the tactics of Canadian diamond producers as a business template.

Exploration at Regal Ridge will continue in 2004, and True North intends to apply the techniques it is developing there to other deposits, and continue to encourage others to do the same.

At least three other exploration outfits have heeded the call. Firestone Ventures Inc., Hinterland Metals Inc. and International Arimex are active on claims around Regal Ridge, and True North itself has reported finding emeralds on its Ghost Lake property in Ontario.

It’s still premature to know for sure whether the Yukon is going to do for emeralds what the Northwest Territories has done for diamonds. But if it does, it will mean that the prospectors who explored the Yukon for gold, silver, base metals and even diamonds since the Klondike gold rush over 100 years ago, may have missed the real treasure all along.

Ron Hall is a metallurgical consultant and freelance writer based in Vancouver, B.C. He may be reached at minmet@canada.com.


Print this page

Related Posts



Have your say:

Your email address will not be published. Required fields are marked *

*