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Archive for July, 2008

An experience of the northern rockhound culture

gemboree1 008, originally uploaded by Mic2006.

Ontario rockhounds look forward to the Bancroft Gemboree, it is the biggest rock and gem show in Canada. I have taken a week off work to attend the gemboree and visit various rock collecting sites up in that area.

In my book (as of yet unpublished but still under review by a publisher) I write about the experience of the Bancroft Gemboree. There is a distinct division between the merchants inside and those without. As for deals – you are most likely to get a good deal where the dealers are not professionals. As I wrote …

“These outside dealers of rough stone and mineral oddities are shaggier and rougher than the smoothly coiffed gem merchants within. They are often amateur; this pursuit of beauty is their life’s calling, but not their full time job. It’s not about cash; it’s the love of rockhounding that drives them.

An aged lapidary was selling his polishing equipment. On a table beside him he had an archaic buffing wheel. He was willing to part with it for a mere $250. All around him he had 3-litre strawberry baskets filled with cut agate. I bought one on a whim and upon closer examination back at the cottage I regretted not buying more. It was an incredible mix of sliced nephrite, chalcedony, banded agates and jasper. There were all sorts of striped and spotted rocks, cabochons and nodules of every type, an absolute treasure-trove for $10.

“Why dump this beautiful stuff at such a low price?” I asked. Leaning on the table he smiled sadly at me, watery red eyes suggesting long hours at the grinder. “I’m getting on in years you know.””

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Dangerous Ontario cave

IMG_7591, originally uploaded by Mic2006.

The thing with Marmora is that you need to get a feeling for the sinking and resurging channels. Here we are walking up a section of stream bed where the water resurges strongly in the spring from a blind valley. The valley is fed by a number of tunnels. At this time it is possible to explore the tunnels as they are mostly dry but when the water is high – no chance.

The Marmora Maze caves switch back and forth beneath a low escarpment somewhere off in the bush. Josh (my son) and I, had long suspected the existence of tunnels there and one Saturday morning we dug away the debris beneath a joint to open a passage into the maze caves.

The Marmora Maze cave consists of tunnels that have only been explored a little in either direction, both up and down stream. It would seem that the tunnels upstream are low and trough-like beneath a rocky shelf, while down stream there are deeper trench-like passages.

The rock of the area is the Bobcaygeon Formation – rich in fossils, namely some pretty sizeable cephalopods. A couple of years ago we had visited the area with some Russian cavers and one happened to be a specialist in Cephalopds. A cephalopod is like an ice cream cone in appearance, chambered through the cone and with tentacles coming out of the top of the cone.

The entrance to the Maze Caves looked pretty unstable today, a good bump will likely to bring several tons of rock down on your head. I think the entrance needs re-digging before anyone enters there again.

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Rimstone dams and other natural wonders

IMG_7528, originally uploaded by Mic2006.

Another picture of the shelves to either side of the main tunnel of Spanky’s Paradise. The rimstone dams are especially white and pure. It would appear that they have formed in shallow troughs that once held flows of water that are a lot more vigerous than now.

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Spanky’s Paradise – beneath Marmora’s rocky table

IMG_7552, originally uploaded by Mic2006.

There is a lot of calcium precipitation in this area of Spanky’s Paradise – little soda straws forming, rimstone dams etc. One caver who had crawled somewhere that maybe they should not hae said that he had seen cave pearls and another claimed to see sunken calcite rafts. Not having been into heavily decorated section I have not seen those.

If there are formations in a passage it is not unreasonable to suspect that the excavation of the tunnel in that area by running water has stopped. Formations tend to be up near the roof and above waist height, the floor of the tunnel is V shaped – it suggests that running water still scours the bottom of the tunnel but seldom reaches up high.

There are a couple of theories out there on cave formation. Some thinking souls suggest that caves were formed when the water’s of the Great Flood flowed back underground, but scientists usually revolve around the idea of a muti-phase development. Generally speaking there is the idea of formation beneath the water table – resulting in rounded and eliptical shaped tunnels, then formation above the water table – brings on trenches and v-shaped tunnels and lastly – infilling by reprecipitation.

In a nutshell, the solution of calcite takes place by the erosive effects of carbonic acid and its reprecipitation takes place when a super-saturated solution looses carbon dioxide to the cave air. This “gassing off” diminishes the ability of the acidic solution to hold dissolved solids and so they are dropped as cave formations. A splattering droplet falling from the cave ceiling looses carbon dioxide, as water flows over the edge of a rimstone dam it looses Carbon dioxide etc. etc. Solution increases in cooler temperatures and beneath a vegetative cover – thus in heavily vegetated karsts that are slightly buried, cave formation is accelerated.

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Marmora Caves

IMG_7567, originally uploaded by Mic2006.

As mentioned yesterday, we had hoped to connect the joints under the escarpment by following across a wide/low shelf that was clear of formations. I followed along in the shelf, aligned more-or-less with a shallow v-shaped trough where my belly fit just right (you can see the trough in the picture just beneath my chin). It looks like something maybe around the size of a fox must spend some time down here (lots of droppings and bones).

Unfortunately, what looked like a going passage from a distance turned out to be not much at all when I got there and here I am at a pinch that goes no further for a person of my size. I had not reached the intersecting joint that I had hoped to reach but still realize that there are numerous likely crawlways that might lead on to that. As for now – Sunday morning – my arms are killing me, I could barely struggle out of bed.

If every lead opened into cave we’d be in West Virginia!

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Looks like something from the innards of a cow

IMG_7576, originally uploaded by Mic2006.

The cave that we already knew of – lets call it “Spanky’s Paradise” as a working name (subject to change, but convenient for discussion), was new to Jeff and so we wandered around a bit, photographed and generally absorbed the bone numbing cold from the rock.

At a certain point the tunnel jogs sharply to the right and there are rimstone dams all round. The tunnel forks shortly after this and to the right there is a narrow cleft that makes for treacherous crawling. To the left there is a trough, swept free of formations, likely a conduit for water at some time of the year. We resolved to continue on for some distance at a later date – possibly along the cleft as it seems to open out a bit further on and if we can hit a tunnel running perpindicular we are on a one way trip to wonderland.

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Approaching the tunnels through the mist and water.

IMG_7518, originally uploaded by Mic2006.

Our intention today was to push one of the tunnels in the area that I knew might go on to other unexplored passages. Most promising is a low escarpment into which burrows several joints. There are three joints that can be followed (the narrower ones) and several other wider ones that have their entrances filled with humus and stones. I suppose the wider joints got to wide but if the narrower joints lead to incredible beauty – imagine what the wider joints lead to!

The joints are connected intermittantly by wide shelves beneath the surface, at times choked by flowstone and stalactites – floored by rimstone dams. Alternately there are also sections of the shelf that are low but barren and we had theorized that maybe we could reach one of these buried joints by wriggling along a shelf.

We approached the underground tunnels along a joint that – like many in the area – was open to the sky. Jeff led the way, beneath the moss and through the mist.

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