East Bay Regional Parks is having an open house April 5-6 for the silica/sand mine tours at Black Diamond Mines Regional Park, where you’ll be able to go 810 feet into the mine rather than a mere 400, which was as far as folks could go last season. The open house is noon to 4 p.m. both days. Click the link for more details. I wanted to check out the mines earlier this year but they’re not open in the winter. Should be lots of wildflowers happening up there too, with all that open grassland and sunny hillsides.
Here’s a picture down into one of the shafts at Black Diamond Mines (not part of the tour, I presume):
Black Diamond Mines is around here: