Oakland Geology

This former quarry in Laundry Farm encompassed the ground now occupied by Belfast and Bermuda Avenues, just south of Horseshoe Canyon and Leona Heights Park. One source, the Laundry Farm map, shows something called the Hotel Mine in this area but I have found nothing about that mine, only information about the Crusher Quarry. It was operated by the E. B. & A. L. Stone Company around the turn of the last century. In 1906 the state mineralogist reported about this quarry: “Reddish, decayed rock is hauled from face without crushing, and used for sidewalks, etc.” The name came about because the site was next to the crushing plant.

Here’s where we start, at this fire road just north of Bermuda Avenue off Mountain Boulevard.

The square object is the upturned west end of a long, arcing concrete ramp. It slopes down to ground level and levels off beneath some oak trees.

Then it turns up again, as if aiming at the old quarry face.

Here’s the broken upper end.

This was once the working middle part of a cable tramway, a set of steel cables that carried huge buckets back and forth between the rock face and the ground. The ramp therefore describes a roughly catenary curve corresponding to the natural sag in the cables.

Onward to the high working face of the quarry.

This is highly fractured Leona volcanics that needed little processing because it was already naturally half-crushed. The name of the quarry may be typical 19th-century American irony.

The stone has acquired a typical blushing orange hue because it releases a lot of iron, which oxidizes and hydrates forming thin crusts on exposed surfaces. The large deposits of red and yellow ocher in this area, which were widely known among Bay Area native tribes, arose from many thousands of years of uplift, fracture and weathering of this rock.

Higher on the hillside above the quarry, you can find lots of natural outcrops. They show signs of working in places. I think the stone has a nice presence.

You’ll see sheltered spots with the glimmer of various shades of ocher; also evidence of wildlife.

On the way back out, take time to see what’s blooming in the raw land the quarry left behind. These are called red maids.

And the fine gravel even supports an underground ecosystem that produced this emerging mushroom.

The locals enjoy and watch this place, so there isn’t any tagging or bottle-smashing to speak of. Climbing is dangerous; stick to Berkeley’s rock parks for that. Visit discreetly and leave the place cleaner than it was when you came.

This entry was posted on 11 April 2015 at 5:31 pm and is filed under Leona volcanics, Quarries and mines. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.