Since the shutdown I’ve been scrupulous about going out only on essential business. Yes, my idea of essential is wandering around with one eye on the ground, the other on the landscape and my mind in the clouds, but it’s not really essential. Basic, baseline exercise is essential, and I can get that in with a walk of a mile or two.
That said, a walk of a mile or two can take you to lots of interesting places no matter where you live. The upper part of Fairmount Avenue is within that perimeter, and that’s where this stone wall caught my eye. Oakland’s houses of a certain age occasionally feature our local blueschist, and this is a particularly striking example.
Just a few feet farther, the scope of the work emerges.
The entire front of the property, plus the long stairway to the entrance including the risers, employs this stone to dignified effect.
Blueschist can be garish, but here it complements both the concrete and the Craftsman house in color and texture. I took a close look at it to compare with its appearance at various Oakland locations. The stone is unusually sound and was apparently quarried for this purpose. I don’t think rock yards carry this kind of unfashionable stone today — it’s hard to source large, consistent quantities, and artisanal stonemasons are no longer as plentiful as they were a century ago.
I don’t know any commercial sources of rock like this, although it’s conceivable the old Hutchinson quarry in El Cerrito, where the recycling center is today, used to yield some from its upper level. I suspect it came from a pit in the Crestmont/Serpentine Prairie area. This big exposure on Old Redwood Road shows the general quality of the rock up there.
Some of the rock in Crestmont is a pretty close match, but in general it’s more fractured and pocked with carbonates.
I suspect, but have no way of proving at present, that this old pit at the back edge of Serpentine Prairie was the source. Our serpentinite/blueschist isn’t useful for crushed stone, and although “a few tons” of poor-quality asbestos was once mined up here, this particular rock has no sign of containing tempting amounts of chrysotile. So that leaves decorative stone as the most likely product.
And that reminds me that I need to visit the meadow up there soon, for the exercise.
Oakland Geology 
24 May 2020 at 2:02 pm
Beautiful photos and writing–thanks!
17 May 2020 at 10:08 am
The SFPUC quarried a lot of blueschist for the Calaveras Dam Replacement project in Sunol. It is indeed a beautiful rock- and does contain asbestos. Workers were required to wear respirators while working in and around it.
11 May 2020 at 7:05 pm
That’s a nice discovery. Have you looked for a way to send a note to the homeowner? Sometimes they know more than you might expect, especially in a case where whoever built those stairs cared about how the end product would look. In any event, thanks for the diversion.