Oakland Geology

There are three stone circles — little henges — on Lakeshore Boulevard, one near El Embarcadero by the library and two up near Mandana. They all have the same stones, supposedly from the same source.

The first one we all know, but maybe not its name: Astro Circle.

It’s a large ring of stones in Eastshore Park, 120 feet across, with a tree, swings, slides, a water fountain and a nice new toilet on the sidewalk. It was dedicated in 1968, at the height of Apollo fever, and sported various space-related features including a steel “flying saucer” made from a boiler tank by the city parks department. (Read more over at the Oakwiki.) Also this concrete “moon cheese climber” that if anything has gained in charm over the years.

The other two, in skinny little Mandana Plaza Park, on Lakeshore between Mandana Boulevard and Prince Street, are much smaller.

The plaque there, placed in 1958 by the local Kiwanis Club, calls the two rings a “Creative Play Area.” The installation dates from the same period as The Thing in Lakeside Park, when progressive thinkers were reimagining children’s play as vehicles for cognitive and physical enrichment. A Tribune article from the time tells more about the scheme, which was called “Just Imagine!” and originally had three rings and a much more elaborate set of features. Does anyone have old photos of these things?

But yes, I’m here to talk about the rocks. All three circles are made of large blocks of cut and dressed sandstone. Specifically, it’s a medium to coarse grained lithic arenite (mostly clean quartz) with sparse gravel clasts. The grains are angular and subangular, suggesting a nearby source in granitic basement rocks. This block at Astro Circle displays a large mudstone clast; others feature small siliceous pebbles and holes where shale clasts apparently eroded out.

It’s decent material, not good enough for monuments but quite adequate. The blocks are expertly dressed, to judge by the tool marks, and were clearly salvaged from a demolished building.

The newspapers report in both cases that these blocks were once part of the old Oakland High School (1871-95), and were supposedly brought “round the Horn” from Indiana.

It’s plausible that they came from Oakland’s first high school, a fine old building at Market and 12th that the city was very proud of.

^{Bancroft Library image}

The stones would have come from elements of the experior like window ledges, pediments, lintels and archways. Most of the building was probably faced with timber. I’ve found no record of its construction details in the newspapers.

It’s plausible that the parks department rescued the stones and left them in a boneyard for sixty years until the enterprising Amedee Sourdry found a new use for them. (I think his agency was behind the recycled boulders of Lakeside Park, too.)

However, I can’t vouch for the bit about Indiana sandstone coming by sea around the Horn, especially (as some say) in the form of ship’s ballast. I don’t know enough yet to say for sure, but Indiana was more of a coal-producing state than a stone-quarrying state at the time. I also can’t quite square the character of the sandstone with the geology of the state. It’s more like a California-style sandstone.

I also feel skeptical about the economics of producing this not-quite-premium material, then shipping it to New Orleans for a long, perilous sea voyage to California. The transcontinental railroad was finished in 1869, so the school’s architects more likely arranged for a load of finished stone to be fabricated to order and delivered by rail. Maybe even from Indiana. It would be bragworthy.

Just stuff to ponder as I sit and watch the kids play on the moon cheese climber.

This entry was posted on 14 November 2022 at 8:01 am and is filed under Oakland stone. 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.