Monday, February 23, 2009

Monday Minerals: Fluorite, Calcite, Apatite

Back in January, I mentioned (and showed a sample from) Cobalt, Ontario. Toward the end of that post, I also mentioned Bancroft, Ontario, which has an amazing set of mineral occurences- an incredible variety, and stunning quality, spread out over a few tens of square miles. I used to have a number of maps and field guides to the area, which I have visited a few times, but they have been lost, along with most of the pieces collected there, through various disasters. I have not really found any good on-line sites either; most of the pages I've found are spectacularly uninformative.
I don't remember the name of this quarry, but it was one of the farthest west sites shown on the collecting spots map I had. It was a flat fee site; as I remember, it was $4 (Canadian, in 1988) to enter and collect whatever you wanted. No per-pound cost.
The two obvious minerals here are fluorite (purple) and calcite (white). The actual occurence was fairly restricted, a lens-shaped outcrop that looked like a boudinage structure, about 10-12 feet through at the thickest, and about 3 times that across. The odd calcite-fluorite "marble" appeared to be fault-bounded, and encased in Grenvillian gneiss/schist above and below. The two really spectacular minerals here were apatite and hornblende; sadly, I don't have any of the really nice specimans of those anymore, but individual crystals of those two were up to 3-4 inches in diameter, and up to 18 inches long. In the crop (below) from the above picture, you can see a cross section of an apatite prism in the lower right corner.
I think I still have a ragged piece of hornblende from this site as well; I'll try to find it and run it another time.

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