Geo 730: September 3, Day 611: Adit

 According to Wikipedia, an adit is "entrance to an underground mine which is horizontal or nearly horizontal, by which the mine can be entered, drained of water, ventilated, and minerals extracted at the lowest convenient level." Above is a nice example, which, sadly, is no longer open to explore. In the diagram below, I've sketched out (from memory) the rough layout of the mine. The diagonal checks indicate areas of particularly intense brecciation- though all the host rock has been through multiple episodes of shattering and recementation. The breccia zones are exaggerated in width for clarity and continuity- the width of the addits more accurately represents the brecciated zones.

So the opening, shown in the top photo, is clearly where they started. My guess is that the miners started there, working back along the fault zone. I suspect they had identified the second fault zone at the outset; it's pretty easy to find, even with moss and other plant growth obscuring it. The first leg provided enough payoff to keep them going, but slowly started getting poorer. So they dog-legged over to the second fault zone, which, again, provided enough gold to keep them going a while, but also got poorer as they went along. At that point, they sent exploratory adits to either side, one back to the original zone, and a second to a possible third zone in the other direction. I have not been able to identify a third zone on the hillside, and all the rock in the tunnel is so torn up that it's difficult to make out anything with confidence. So that third zone may have been based on observations I haven't replicated, or it might have been a hopeful guess on the miners' part. At any rate, it was a lot of fun to talk with kids after they'd had a chance to get a feeling for the layout about why the miners had chosen to tunnel the way they did. Obviously, from the modern day, we can only speculate, but the story above makes good sense.

Photo unaltered. August 5, 2012. FlashEarth Location. (Park in pull-out here, walk back down the road a bit, and look up hill to right.)