Feeds:
Posts
Comments

Archive for May, 2007

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.

Advertisements

Read Full Post »

I had recently been corresponding with one of this province’s cavers – James Sled, he has told me of a cave that sounds really promising – a pit on a high ridge in prime caving country. The pit is situated in the bottom of a 15 foot wide depression and beneath a river runs along a tunnel that eventually sumps.

Using the patchwork of topo maps that I was able to download from toporama and James’s directions I think I have managed to pinpoint the exact location.

At this time my good caving friend is recovering from an operation. I typically conduct my explorations with him. I am holding off the initial reconnisiance of the pit until he is in better shape – by the sounds of it his wound is supperating and I have suggested he calls a doctor fast – lets hope he does.

One the bright side I have just had my article on “Costa Rica River Travel” accepted by the New Zealand Herald, cant wait to get it in print. I am considering another travel article on the plight of Costa Rica’s howler monkey’s. In the town where we were staying (Tamarindo) they average two a day being electrocuted on the power lines. I think I will discuss that sorry situation in my next post. Mick

Read Full Post »

IMG_6361, originally uploaded by Mic2006.

Here is something that we are likely to see less and less of with the accumulation of greenhouse gasses.

Living in a cold climate with somewhat restricted caving opportunities the ice formations are a special treat – though – keeping in mind, the bats hibernate through the winter in many caves and so dont cave in known bat caves during the colder months – waking bats at the wrong time could kill them.

The above spike towered up beneath the surface well after the surface snow had melted. My caving partner and I made a late spring exploration in one of our favorite caving areas to enjoy this unusual phenomenon.

In alpine and polar regions cave ice develops much as it would under regular circumstances however the formation of temperate region cave ice is a more complicated process.

In a multi entrance cave that has entrances at different elevations the air flow changes with the climate. In colder months the freezing air is drawn through the lower openings and vented out the top. In the summer the process is reversed. Obviously there needs to be a greater flow of cold air through the cave than warm, hence, “A colder climate than the temperature” (Emil Silvestre – Perennial Ice in Caves in Temperate Climate and its Significance) – though sadly as has been pointed out, there is no longer such a thing as temperate caves that are showing an increasing balance of ice accumulation – everything is melting.

Where I live – an area once referred to as “The Cave Desert” there are many examples of “the ice box phenomenon”. The Niagara Escarpment is riven by deep crevices and they act as pools where cold air can accumulate and preserve ice well into the summer months. The cold air trap is most usually found in single entrance caves that dip down at a steep angle – eg. a crevice cave. Cold air slides down as it is heavier and warm air is pushed out the top of the shaft. The entrence to these ice box traps needs to be large enough to allow a suitable exchange of air to overcome the “geothermal flux” – the rock is in need of constant cooling from above as it maintains its own ambient temperature from the crust beneath.

Read Full Post »

IMG_6699, originally uploaded by Mic2006.

In the sci-fi movie, “The Descent”, Webster’s Falls formed the backdrop in one of the scenes. Lava poured over where water now flows. In polar contrast, the real beauty of the falls is revealed in winter when the scree beneath is coated with ice. From above the rubble looks like a great bunch of frosty grapes and all around the icicles hang in glittering adornment. Approaching the face is especially treacherous at that time.

Summer is the best safest season to explore the inner wall at Webster’s Falls. This gentleman followed me around the edge of the cascade and into the niche worn behind the curtain. Because of the caprock on top of the falls – a more resistant material – the falls are neatly slotted into the “Plunge variety”. Read Mark Harris’s book “Waterfalls of Ontario” if you would like a really engaging discussion on the subject. If you want to know more about Ontario’s rock or caves read my book, “Rockwatching; Adventures Above and Below Ontario”.

Underneath the sound is deafening. The water drops from 72 feet above and though the volume is but a fraction of what it once was you are left awestruck by the natural energy. It is a cool, dim world back there. The ground is slick with the pinkish paste of decaying Queenston Shale. I shade my camera lens from the spray and attempt to find those spots in the churning air behind the curtain where the quantity of spray is less. None-the-less I am soaked within seconds.

Read Full Post »

IMG_6684, originally uploaded by Mic2006.

Climbing along the edge of the valley you soon reach the base of the falls. These hooded figures looked a little sinister – something rather grim taking place – but in truth they are just youngsters enjoying the scenery.

Read Full Post »

IMG_6682, originally uploaded by Mic2006.

The bowl beneath Webster’s Falls – a rather earthy hue with great slabs of fallen rock and vegetative drapery hanging down the cliff walls was made bright and gay by the visit of a large family of Indians. In silk saris the ladies clambered across the rock. By their facial expressions they appeared to be not so enamoured by their visit. Young girls shed their bejewelled sandles amongst the slimy puddles to scramble forward into the misty breeze.

Kor (a scientist) studied several erosive bowls that he was able to identify along the Logie’s Creek branch of the Spencer Gorge. (Webster’s Falls is on the Spencer Creek branch of the canyon) The largest bowls were those that were the furthest downstream. (350 meters wide by 60 meters deep) In size they are comparabile to Niagara’s famous Horseshoe Falls amphitheatre. This progression of bowls (in diminishing size) up to the present day Tews Falls is indicative of a watershed that is drying up. What were once great roaring cataracts of fearsome proportion are now just delicate silvery curtains.

Read Full Post »

IMG_6697, originally uploaded by Mic2006.

Being interested in the local geology and desirous of a little trip this morning, Maggie, Chester and I headed southwards from our Guelph home toward Hamilton and the famous Webster’s Falls.

I recall my first discovery of this feature some years ago when I had visited the nearby town of Dundas – looking for the infamous “Satan Tunnels”. I had been speaking to the lighthouse keeper at the mouth of the Hamilton Harbour. He had told me of a memory from his youth, tunnels leading into the clifface above Dundas – crowded with abandoned quarrying machinery and on one ocassion where he saw satanists sacrificing a goat.

Scouring along the clifface I had followed up a gorge which eventually branched, one arm following up Logie’s Creek to Tews Falls and the other up Spencer Creek to Webster’s Falls.

Webster’s Falls (as pictured above) displays an interesting crossection of the local geology. As can be seen it is a two tier’d falls, the step being marked by the resistant blue-grey limestone of the Irondequoit Formation. Though here it is but a narrow ledge that crops out, Balls Falls, some 30 minutes drive along the escarpment edge displays the ledge as two distinct waterfalls, several hundred metres apart – Upper and Lower Balls Falls.

Read Full Post »

Older Posts »