Archive for the ‘Oakland stone’ Category

Rocks in the gutter

9 May 2022

Down in the Chinatown and Produce District area, we have some special rock-lined gutters, ranging from fine . . .

to funky. They’re the nearest thing Oakland has to cobblestone streets, and they serve the same purpose: heavy duty traffic.

The variety of these gutters suggests that they were emplaced over a long period, under various city contracts. Given that, it’s probable that the stones come from several different sources. But nearly all of them are basalt, the fine-grained, gray to black lava erupted from volcanoes up and down the western states.

These days basalt is a fancy stone, as seen in finer landscapings like the courtyard of Berkeley’s new School of Public Health building. These are natural hexagonal cooling columns of basalt, like those up at Devils Postpile in the high Sierra, cut and polished for elegant seating.

But our gutters are lined with prosaic basalt. And I think some of it came from our own hills. The Sibley Volcanic Regional Preserve includes the grounds of several former quarries that produced basalt rock. In 1906, State Mining Bureau Bulletin 38, The Structural and Industrial Minerals of California, reported on the first of these, the Ransome Quarry: “This quarry is on the Old Fish Ranch road, about 5½ miles from the Oakland City Hall. It was opened in April, 1904. A tramway 600 feet long carries rock from the quarry face to the crusher at side of road. The rock is a fine-grained basalt, and is used for macadam and concrete. Some gutter rocks are sorted out. The rock is hauled to Oakland and Berkeley by wagon.”

Sibley’s lava flows aren’t the enormous, massive ones of Oregon and Washington’s Columbia River Basalt, a genuine Large Igneous Province widely attributed to the hotspot that now underlies the Yellowstone region. The Sibley volcano is a dinky thing with a lot of different deposits ranging from ash beds to proper basalt.

I like to think that a couple workers up there kept their eye on the rock and picked out good bits for this premium trade. I imagine that those are the rough gutter blocks. The later street contracts probably used more economical, higher quality material from farther away, like the North Bay counties or even Black Butte up near Orland.

Nowadays, for better or worse, we keep it simple and use concrete or asphalt, even though the work needs more repairs.

McAdam’s quarry

11 April 2022

One of my first outings during the pandemic era was a hike up Shepherd Canyon in search of Alexander McAdam’s sandstone quarry. But I was missing a telltale clue. Now I think I’ve found it.

I wanted to locate the quarry because it produced the stone used in the historic First Unitarian Church in downtown Oakland, the only example I’ve found of a truly local rock used as dimension stone in a building instead of crushed stone in an anonymous construction.

The clues I had pointed to a location “at the head of Thirteenth Avenue” somewhere “in Medos Cañon, back of Piedmont.” I thought this meant some place in present-day Montclair, but all the old maps I checked didn’t show any land there belonging to McAdam. Then I tracked down the 1894 Wagner map of Alameda and Contra Costa Counties, and here’s where his ranch was: over the ridge above Shepherd Canyon, in the valley of Redwood Creek.


Shepherd Canyon in the center; the old Thorn Road runs around its north edge. The Heyland property at lower left is in Dimond Canyon and the Hays School is in present-day Montclair. The McAdam property is at lower right past the county line, shown by stippling.

The land is within Redwood Regional Park, so I surveyed the territory last week. Here’s a closeup of the map, showing McAdam’s 131.24 acre holding.

And here’s where it sits in the geologic map.

This is very steep country, in an area where the redwood groves had been logged out forty years before. McAdam used it as ranchland, like others in this remote district, but he also operated a successful quarry here somewhere. It wasn’t in the coarse, crumbly Oakland Conglomerate (mint green) or the shaly stuff of the Shephard Creek Formation (pale green), but somewhere in the thick-bedded, fine-grained sandstone of the Redwood Canyon Formation (Kr on the map, olive green).

Fortunately, Redwood Regional Park maintains the old trails and logging roads, so I superposed McAdam’s land on the park’s trail map and gave it all a good look. Note: the poison oak is very healthy this year.

The only place a quarry would make sense is at the very top of the property, but if you’re up for it, the Tres Sendas trail takes you down to some nice woods.

The rock here is appropriate, just like the stone in the church.

And some of it fractures nicely enough to be dressed into ashlar blocks.

But it would be nuts to operate a quarry down in the back forty. Up on the ridgetop in the northwest corner of the land is where I think McAdam had his pit. It’s the backdrop of this view over the spot where McAdam’s ranchhouse was, at the westernmost corner where the Waterloo Staging Area is today.

It was accessible via the Castle Canyon road, as seen in the 1897 topographic map. The McAdam place is in the center, at the end of the road.

The hilltop is just off high-lonesome Wilton Drive, where I last took you three years ago for the Shepherd Canyon circumambulation. The views from there are still wonderful.

The slope immediately below, too steep to think about descending, is where I think the quarrying went on. The outcrops of Redwood Canyon Formation display good rock.

I’m glad to put this little mystery to bed. And if the Unitarian Church must replace its stone with authentic materials, they know where to look.

Art concrete at UC Berkeley

28 February 2022

I have occasion to walk through the UC Berkeley campus often, and there’s a lot there to see. Recently a subtle feature caught my eye at Morgan Hall, which is otherwise a pretty undistinguished building — this rich concrete screen that borders its brick courtyard.

It does a lot of work in a discreet way.

The ten panels of rugged dark concrete, identical but alternately rotated, are laid out like a Japanese folding screen. They form an effective barrier, but the visual impression is of lightness and transparency. Two small accent panels of polished colored concrete individuate each frame. Rounded benches on the inside invite a closer visit.

The eucalyptus trees in the courtyard offer organic forms that play off the surrounding hardscape, and the accent panels reward close inspection on a sunny day. They aren’t run-of-the-mill gravel. The colors are precise.

The brisk grain boundaries and crisp polished faces, one random and the other geometric, tease and please the eye.

The blends of clasts and matrix are tightly controlled.

And what is it about that dark gray framing? Look close in good light.

Not only is it sprinkled with light grains accentuating its darkness, but the dark rock is shot with color, the deep green and blue glimmer of pyroxene minerals and serpentine. A real artist made this. I wish I knew who it was.

Two women named Morgan left their mark in Berkeley. Agnes Fay Morgan (1884-1968) was a pioneering scientist in the field of nutrition who during a long career at UC Berkeley (1915-1954) rose to the head of its College of Home Economics. (The other one was Julia, the architect.) She was widely celebrated as a founder of nutritional chemistry and a person of influence. The Berkeley Chemistry Department recalls that “Dr. Morgan’s teaching was characterized by enthusiasm for her subject, clarity, and a seemingly boundless energy. She had a sublime confidence in her rightness and a genius for disregarding nonessentials and relaxing when the opportunity presented itself.” Morgan Hall, built in 1953, was renamed in her honor in 1961. I can’t help but think that Dr. Morgan indirectly influenced my own mother, who earned a Home Ec degree from Cornell University, another progressive school, in the early 1940s and put it to full use raising and nourishing six children.

Rock garden coming to Lake Merritt

29 March 2021

The Gardens at Lake Merritt are building a rock garden in the heart of the grounds. They have plenty of gardens with stones in them already, but this will be a proper rockery. This post is about the work in progress. I know almost nothing about the plants they’ll be featuring, but I do know a little about rocks.

As we enter yet another year of drought, it’s important to note that rock gardens are made to conserve water. The stones and gravel offer solid shade to the underlying soil, and the typical plantings are small, hardy species from alpine or desert settings. As you bend down to admire these plants, have a look at the stones.

The location is between the community plots and the Torii gate, the crossroads of our remarkable garden complex. Just across the path is the hill-and-pond garden, where the turtles hang out.

This view toward the lake shows the layout. In the background is the entry to the Sensory Garden, which has had a thorough going-over during the shutdown.

The foreground containers in both photos showcase rounded river stones, blue-green argillite most likely from the northern Coast Range. I would not be surprised if some of the rock nuts of the Suiseki Societies of Northern California contributed to this project.

The center of the garden is a mound of sandstone tablets, with some accent stones, oriented north-south for optimal sun. Rings of different colored gravel surround it. Note the “do not climb” sign.

Some of the basins echo the brown sandstone of the central mound, offering textural contrast.

Others contrast more strongly. Here rough greenstone is set in crushed marble.

And what would a Northern California rock garden be without some red chert?

All of these rock types are typical of the Franciscan Complex, a lithological scrapple that makes up the bulk of the northern Coast Range, including San Francisco and the hill that Piedmont sits on. Get to know them, and you’ll see them all over the place.

The Gardens at Lake Merritt have several sectors that artfully mix plants and stones. The water garden I mentioned earlier is one, and there’s the cactus garden and the bonsai garden (which has just added a suiseki section) and the enclosed Japanese garden by the Community Center building. They’re all looking great right now, but check the hours before you go; weekends are still closed.

A few years back I wrote about the remarkable rock garden assembled by Ruth Asawa in San Francisco. As the world reopens, I hope to visit it again.