Sarnac Zircon Mine - Where the Lure of Crystals overpowered our Fear of Bears - (temporarily)

IMG_1272, originally uploaded by Mic2006.

The Sarnac Zircon mine was undoubtably one of my stranger “rockhounding experiences in the Bancroft area. The approach was through the bear-ravaged Monmouth County Dump. Tripping down a stinking wave of torn blue garbage bags we wandered along what could only be describesd as a “bear’s highway”, all scat-strewn and gouged by claw marks beside a wall of impenetrable bush. Dark tunnels within this barrier could only have been made by vast hordes of bears on their nightly visits to the dump.

The zircon crystals at the dump location are found in a narrow valley that is overhung by thick bush. I wormed my way up to the digging face sheltered beneath an overhanging ledge. As you worked the sand showered down in a dusty cascade. It brought back long-buried memories of my adolescent “sandbox wars”, a malicious playmate throwing grit in my eyes. It must have been some squabble over turf and Tonka Toys.

With the exciting prospect of finding gem crystals I managed to ignore the physical discomfort and set myself to the task of tunnelling into the pegmatite vein. As I worked it felt as though there were giant spiders crawling across my neck. I swatted wildly but the sensation was imaginary, it was only the feathery caress of tree roots, a fibrous gauze veil that screened the front of the overhang. With my wooden handled mason’s hammer I swung into the soft decaying rock. It was like chopping into a mouthful of rotting teeth, crump, crump, crump.

Maggie and I had travelled here on this dripping, grey morning to hunt for zircon. Saranac Uranium Mines Limited had excavated the site in the mid 50’s and the discovery of zircon had been incidental to the search for uranite and other highly sought after radioactive minerals.

A zircon crystal generally appears as an elongated prism with a pyramidal termination at either end. I found it difficult to pick undamaged specimens from the rock. My extraction methods were rather crude. Pestered incessantly by a fearful wife I burrowed away, possibly with more haste than care. Maggie wriggled in behind me as the pegmatite crumbled beneath my hammer. I suspect she considered it to be safer than in the bear-infested woods. Helpfully she pointed out a well-formed glassy block of zircon. I managed to pry it loose. It was a whole prism of smoky brown crystal; far more translucent than I had expected. With Shaka’s arrival and attempted entry into my workspace I had to evict them both. The cramped conditions made it almost impossible to work.

When zircon was found as a colourless stone in Sri Lanka, locals, without our modern understanding of chemistry, believed them to be inferior quality diamonds. Because of their extreme lustre and the scintillating rainbow of colour that dances from the cut stone, the mistake was quite easily made. A zircon varies widely in weight and refractivity and because it’s hardness can change throughout the stone it is often difficult to polish. A gemmologist can quite easily distinguish between a colourless zircon and a diamond, as the light rays that enter a crystal of this nature are quite widely split. This property of being “doubly refracting” is present in most gem stones, but to a lesser extent than appears here. The diamond does not have this doubly refracting property as it is from the one crystal system that does not split light: the cubic crystal system. When looking through the crown of a zircon at the pavilion facets, every line in a cut zircon will appear to be doubled.

In Bancroft, many an avid mineral collector sets out to find zircon. It is typically found in igneous rocks such as granite, but on occasion it can also be found as an alluvial material in sedimentary rock. In the case of the Sarnac Mine zircon is found in a granitic pegmatite dyke.

The appearance of gem quality zircon at the now out-of-bounds, York River Skarn was by no means common in the Bancroft area. In his article, “York River Scarn Zone Near Bancroft, Ontario, Canada”, Michael Walter says that with the use of ultra violet light at night, zircon specimens can be seen to fluoresce bright yellow. A mustard yellow fluorescence under both short and long wave light is a feature typical to most zircon crystals. The York River Skarn specimens are most frequently small and white and sometimes found in proximity to far larger, well formed brown vesuvianite crystals. On one visit to the skarn, Michael extracted a large slab of calcite from beneath a ledge. It had several beautiful purple crystals with superb form and lustre. The crystals were within the calcite matrix, doubly terminated, and in one case at least an inch and a quarter long. They were amazing translucent gem quality zircons. It was a find that was unheard of by regular collectors to the site.