New Discovery: Rubies in Nova Scotia

by Hans Durstling

Dr. David Mossman of Mount Allison University in New Brunswick Canada recalls telling his gemology class some twenty years ago, that if he were going to go in quest of precious stone in the Maritime Provinces of eastern Canada he would set his sights on the George River series of Cape Breton Nova Scotia.

David Mossman. Undoubtedly Mossman’s training in gemology and love of gems led him recognize what many others must have often seen and ignored.

For on theory, the formation had what it takes: a complex system of pre-Cambrian gneisses, metacarbonates, schists and granitoids characterized by a very wide range of metamorphic conditions. It was a large series, covering about one fifth of Cape Breton. It was not well explored. And it was the only thing around that approximated the rock types and metamorphic conditions of the gem fields of the far east.

He did not, however, take his own advice. And when at last he did get to do exploration work in that area this past summer, it was not at all in quest of gemstones, but rather for platinum group metals and gold. Among the locations the work took him to was a somewhat well known albeit disused quarry in the Boisdale Hills some twenty miles from Sydney, the formerly industrial iron and steel city of Cape Breton. Dolomitic limestone had been extracted here for some twenty years, from about 1963 to 1983, to be used as flux in the Sydney blast furnaces.

The disused quarry in the Boisdale Hills. A lot of rock was moved from here.

Those details I found out later. It was the third weekend in August at the at the annual Nova Scotia Mineral and Gem Show in Parrsboro on the Bay of Fundy that I first got the hint there might be something intriguing to Mossman’s summer exploration project. He was onto something, he said, a bit tantalizingly, but couldn’t talk about it just yet.

By the end of August that had changed. Look at this, he said, lugging in a twenty pound extra strength polyethylene sack of grey rock and dumping the contents upon my kitchen table. What do you think this is? He pointed to flecks of translucent reddish-purple that stood out like raisins against fine grained somewhat streaky mother rock. The immediately noticeable stair-step cleavage surfaces on the crystal patches suggested feldspar. But one had been broken in such a way that a perfect hexagon outline was revealed. Knowing Mossman’s own fondness for precious stone I hazarded a long shot. Ruby? Yes, he said. Yes it is.

“ I Nearly fell off the quarry walls when I saw what was in that rock,” says Mossman, here with his assistant James Duivenvorden.

Rubies in Nova Scotia? Wow! That was a surprise. Indeed a double surprise, since in such a well known and long worked quarry they must have been often seen, and as often overlooked. As Mossman recalls, it was a case of instant recognition: “I just about fell off the quarry wall in disbelief.” A whole formation full of ruby. Could I isolate some and do some test cutting to assess them for their gem potential? But not to tell anyone.

With that first delivery of rock upon my kitchen table there began several weeks of crystal extraction and subsequent test cutting which was both frustrating and tantalizing.

With a 5 inch “turbo” style tile saw blade in my angle grinder I sawed slits in the talcose, striated, mother rock around the crystals, chiseled the crystal bearing chunks free and ground away the rest of the matrix on the 100 grit roughing out disc of my old workhorse Graves Cab-Mate.

The writer at the Graves CabMate sawing and grinding ruby crystals free of their matrix.  

That was merely dirty and dusty. The frustration began in trying to develop a way to work these fearfully platy, translucent, included crystals into presentable or even passable gems.

Opinions differ whether ruby has a cleavage or parting. Whatever it may have been, the crystals were fearfully prone to part. Most, in addition, were pretty well downright opaque. But some, a few, showed small areas of translucency when held up to the edge of the light. These became the test rough, both for faceting and cabbing. Other chips were cut and set aside for further testing.

Most ruby these days is heat treated in one way or another. Inclusions such as rutile which cloud the stone can sometimes in this way be re-absorbed, enhancing clarity. So, in a rough and ready way, I heated thirty or forty chips from different locations to about 1,800 degrees F overnight in a bed of sand in my old burnout kiln. From this they emerged fritt-welded to the sand grains, and, yes indeed, quite transformed in color. But alas, transformation is not necessarily improvement, and this was the case here. Post heat treatment we had a handful of uniformly opaque bright salmon pink distinctly milky chips decidedly less attractive than when they went into the kiln.

Mossman had meanwhile contacted the noted corundum consultant John Emmett. For him I prepared about a hundred small crystal pieces, maybe half the size of a pea on average, for examination and possible more sophisticated heat treating. Emmett’s initial assessment was that the crystals were so included with boehmite and diaspore that heat treating was more likely to make them worse than better – as my own rudimentary experiment had already suggested.

So that avenue of improvement seemed to be out of the running. I would need to cut what I could as best I could from the better areas of the natural unaltered crystals.

Corundum is a vexing stone to cut at the best of times; and these, so included, so platy, so striated, presented days and days of challenge. The hardness of a single facet seemed to change along the striations leading to parallel zones of undercutting; the edges of the platy zones would crumble under the pressure of polishing and drag scratches across the facet. It was like polishing a harder version of mica in that respect, or like highly compressed cotton candy, which the rough material resembled in color and consistency.

Included, translucent, and miserably difficult to polish. The better rough crystals did in time yield stones that were not unattractive.

The term “low grade rubies” became the habitual designation. But in the upshot I was at last able to develop a polishing protocol that did work – more or less. While it is not likely that the world’s ruby dealers will come beating a path to Cape Breton, still, they are Nova Scotia rubies. And where there are low grade rubies, who can say that there may not, in time, be better ones? Mossman compares the deposit in its geology to an area of Pakistan where similarly low grade rubies were reported for many years, until, at last an area of better quality stones was discovered.

Is there hope? Of course there is hope. In the world of precious stone, there is always hope. The quest for treasure is what fuels the drive. It may be a slight hope, and most likely is. But, as Dave Mossman puts it, “If I were a prospector I’d be looking at acquiring ground to explore.”

From start to finish: an approximately 1/2 carat Cape Breton Ruby brilliant perched beside its rough crystal bretheren.

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