The old Keuhl Lake Mine was actually a small mine that was worked for Zircon Crystals. I'm not sure what the original motivation was but crystals that were collected by scientific institutions resulted in very large, excellent crystals being deposited in most large mineral museum collections around the world.
I have visited the Keuhl Lake deposit many times over the years and have not been able to figure out the geology of the place and whether it would be possible to recover more large crystals in-situ. It is possible, however, to find the odd smaller crystal in the waste rock dumps. So, Daniel and I have gone there several times in 2020-2021, once with Ray McDougall, and recovered a few decent zircon specimens. We had no luck on the last trip and will not return.
The crystals are usually simple elongated prismatic crystals with terminations that show one or two pyramidal forms. No fancy, unusual faces like at some other localities!
Zircon crystals are often fluorescent and such is the case with the Keuhl Lake Zircon crystals. They exhibit a bright yellow fluorescence that is quite startling sometimes!
Zircons are used for age dating rogs in terms of geological time. The study of geochronology. Most people don't realize that the Zircons from Keuhl Lake have been used as the standard around the world for geochronological studies.
Here are a few more pictures.
Here are some images from our recent collecting, the beautiful location and the better specimens.
Keuhl Lake is owned by the Edgecombe Family and is an old farm property. Here is a view of the barn with part of the Lake behind it. Beautiful spot! I found that even on the trips that we found little or nothing, it was still a pleasure to go there.
It is a small lake, no cottages, cabins or boats. Just the two farm houses.
The hike to the old mine site is fairly straight forward, except for a small bridge that traverses a small creek/swamp at one end. The bridge is currently in good shape for people to use. The road at the mine-end is fairly overgrown. On the farm-end, the road is still easily passable.
The only successful technique that we have used was simply to dig in the old waste-pile. All the good zircons that we found were in the top six inches or so, in a fairly confined area which makes us think that, in fact, we were digging in what was probably the "ore" stockpile, at some point. We also had some success by breaking up large boulders but the effort was not worth the reward!
Ray McDougall came with us on one trip. He is always game to get out digging and breaking in the Grenville! Here he is trying his luck in larger chunks near the Lake.
On one trip, we tried to dig in what appears to be a/the pit, in an effort to locate crystals in situ. No luck. Tremendous lot of work to no avail!
Daniel having lunch in the shade during one of the trips. It was in the peak of summer and blistering hot. It is great that the locality is mostly overgrown with relatively large trees!
As is often the case, in the Grenville, we disturb salamanders during our digging. Here is a good sized one!
Here is the largest and best single crystal that we found in our trips to Keuhl Lake. Daniel was sitting on it and shifted to dig in a different direction and... there it was! Good eyes!
The large crystal fluoresces a nice yellow colour. This photo doesn't do it justice. The camera that I was using at the time did not grasp the colour as well, as I'd hoped.
This piece has many, many smaller crystals, mostly in sections of crystals but some excellent ones, as well.
It is strongly fluorescent and the crystals show up so well under SW u/v light.
This piece has one larger, well formed zircon crystal and a number of crystal sections. As well, you can see there are casts of much larger, once present, zircon crystals in the feldspar!
The fluorescent zircons show up nicely in SW U/V light.
I cracked one piece of feldspar open to find a 44mm long, stout zircon crystal inside!
Again, this large crystal exhibits excellent fluorescence.
David and Ray leave the mine area across the bridge. Beautiful day!
Daniel always seems to be in the lead on the way out through the pine forest.