Archive for October, 2013

Actinolite decoration

26 October 2013

I enjoy seeing some of Oakland’s more unusual rock types when they show up in people’s yards. It shows that people like our rocks.

actinbartlett

This boulder of actinolite may not actually have come from Oakland, but it could have. Perhaps a resident spotted it in a streambed and said, “I give this to me.” It’s clearly not part of a professionally assembled landscape package.

Serpentine garden

19 October 2013

This house on Melvin Court has a splendid front yard based on serpentinite: serpentinized peridotite on the right, a serpentine-lined walkway with slate in matching colors, and inlays on the path composed of serpentine medallions. The house itself is painted serpentine blue-green. Click the photo for a big version.

serpgarden450

The Oakmore district is uniformly mapped as Franciscan sandstone, but just a little farther east it’s mapped as undivided Franciscan, so we might expect a mixture of possibilities here. The neat lines on the geologic map are as much hypotheses as they are conclusions. Other outcrops nearby look like volcaniclastic rocks, and some of this home’s neighbors use it effectively. I conclude, though, that this home’s landscape was composed with imported stones rather than assembled from what was lying around. But the rocks may well be Oakland natives from just up the way, perhaps even from the Serpentine Prairie quarry.

Baldwin Street boulder

6 October 2013

Out in East Oakland at the corner of 85th Avenue and Baldwin Street is this fine, underappreciated boulder.

85th-ave-chert

To all appearances, it’s good old Oakland chert, hard at work. I assume it was put here to keep vehicles from cutting across the corner, or perhaps to keep a runaway vehicle out of the building behind it. Who knows? I was just glad it was there to break the monotony. It’s free of graffiti, too.

The other end of Baldwin Street is east of the Coliseum, where it serves as a back entrance for staff and athletes, at the edge of Arroyo Viejo. That’s the creek you cross when you’re walking from the BART station to the game. So between stone and water, Baldwin Street pays more homage to geology than most of its peers.


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