Oakland Geology

One of the cool things about Oakland is its huge variety of buildings, dating from midcentury — mid-19th century, that is — to brand-new. There’s a particular variety of midcentury-20th-century architecture that’s piqued my geological interest: boxy tilt-up structures that I think of as Old Period Safeway, with a cladding of natural rock. In 2017 I showed an example of the type clad in beautiful serpentinite, so I set out to find others around town.

The sharp-eyed folks in the Oakland History Facebook group pointed me to several candidates, and I took an afternoon to visit them and also cruise much of the main roads by Zipcar. Yesterday afternoon I took one more little outing to capture the distinctive building of KP Market on Telegraph Avenue, the best pan-Asian grocery around.

The stone cladding covers only part of the front, and besides it’s painted over. To see it pristine you have to go around the side and look along the base of the wall, where taggers never venture (and thus paintovers aren’t needed).

This is the same coarse-grained dolomite rock used on the iconic Kaiser Center building.

Now for some genuine Old Period Safeways, but first a lament for rocks that get painted over, which permanently spoils them. The former Safeway on San Pablo at 27th Street, for instance, has lost its original appearance beyond retrieval. Without the colors and lusters of natural rock, the walls are unappealing.

But the former Safeway on upper Golf Links Road, in the Grass Valley neighborhood, is unspoilt.

Close up, it resolves as a mixed metamorphic assemblage of river rock, perhaps from the northern Coast Range but the presence of granite amid the sandstone says Salinian instead; that is, from the Santa Lucia or Gabilan ranges around Salinas. I don’t know for sure, it’s just fun to guess.

Another former Safeway, on 14th Avenue at E. 17th Street, still has its stones out.

This wide-ranging river-rock assemblage is darker and more rounded, and granite is absent while lava is present. I peg it as coming from the Diablo Range, but I warn you I could be totally wrong.

There’s one more former Safeway, a dialysis center on Claremont at Clifton, whose cladding still looks good in Google Streetmap but I haven’t visited it yet. The rest of our old Safeways, and there were about 20 listed in the 1969 phone book, are either gone or have been renovated or didn’t use the rock cladding.

One more supermarket and I’ll move on: the Cardenas grocery on High Street.

The cladding on the front side is painted, but on the side you can see it’s an excellent quarry-crushed golden quartzite mixed with lava and what might be travertine or sinter. I’m thinking the northern Sierra here, but that’s a long way to ship crushed rock, even fancy stuff.

Couple more notable buildings, non-Safeways, to show you. Next to the Post Office building off Hegenberger is a low-slung office building, 8475 Pardee Drive.

It’s clad with a selection of river rock I don’t hesitate to call Franciscan sandstone, maybe from Sonoma County.

Finally there’s the Community School for Creative Education building, on International at 21st Avenue. Something about the whimsical accents and the warm, even-textured cladding makes just the right impression.

This stuff is straight crushed quartzite that’s gotta be from some special place in the Sierra foothills, if not farther afield.

Material of this quality can last for centuries, if well maintained.

One cladding type I didn’t seek out for this post is pretty common: big flat hunks of undressed sandstone — that is, flagstone. I have no idea where the stone might be quarried. Some well-known Oakland buildings use it:

But it can be overdone, bringing to mind another fashion, a late-century one: shag carpet.

My knowledge of architecture and the building trades is pretty scant, so if you know the correct terminology for these features, please add an informative comment.

The intersection of Broadway and 20th Street features strong buildings on all four corners. We all know the I. Magnin building (built 1930) and the Capwell (Sears/Uptown Station) building (built 1929) facing it. Across Broadway, we have the metal-clad urban spaceship of the Kaiser Permanente Division of Research building (built 1982) and finally the dark cube of the Golden West Tower Building (built 1968).

One of the nice things about taking the bus is that while you wait, you can look around like architects and urban planners do, as if the cityscape were a stage set. And so, waiting for the 33, I finally took notice of the building wall that I’ve walked past hundreds of times.

It’s chips of dark serpentine, embedded in cement and polished. People in the building trade must know exactly what this is called, but I can’t crack their code. Here’s a closeup.

So all this time, the Golden West Tower Building has been giving the serpentine-clad I. Magnin building a nod, a salute, a shoutout, a heart-tap. I thought that was cool.

That day the 33 took me to Piedmont, where I recognized the same material in Bufano’s “Bear and Cubs” sculpture in Crocker Park, featured here previously.

The other element in that Broadway streetscape is the sidewalk. You’ve all seen it.

This is what’s called a pebbledash finish. Concrete is laid down, then pebbles are pressed into it. When I look at it I think, “What a lovely Franciscan color scheme,” because the reddish and greenish mixture of metamorphosed argillite and chert is so typical of our coastal Northern California rocks. I also think fondly of the red-and-green gravel of Rodeo Beach.

The Lakeside Regency Plaza, 1555 Lakeside Drive, is the 15-story condo building next to the Scottish Rite Temple. Built in 1968, it’s definitely of its time yet of enduring taste. I paid it no mind until a few days ago, when I noticed the four artisanal lampposts that flank its driveway.

In their own way, these are even cooler than the serpentinite cladding I wrote about the other week. The large cobbles lining the shaft are peridotite, a stone that’s rare in the first place and not often usable in the second place. Peridotite (accent on the “rid”) is what the Earth’s upper mantle is made of. Because its minerals are more stable at depth than they are on the Earth’s surface, peridotite characteristically acquires an orange weathering rind as the iron content is released from its olivine and pyroxene crystals. It’s usually shot with veins of serpentine, which degrade its strength.

These cobbles are field stone, not quarried but gathered from the ground in their natural state. They probably came from a riverbed or talus slope in the Klamath Mountains.

The capstones, on the other hand, are lava — specifically, vesiculated (bubbly) basalt like that found in the volcanic Cascade Range. Lava is the opposite of peridotite, to put it briefly, the stuff of the Earth’s crust. These hand-dressed blocks may well have come from northernmost California too, in the vicinity of the Modoc Plateau.

Here’s a look at both rock types in closeup.

Or, of course, inspect the lampposts yourself next time you’re at the lake. I think of them as examples of deeply understated, perhaps even inadvertent, geologic wit.