California’s state rock is serpentine, and in this blog I’ve picked up, photographed and defended it against detractors. I’ve called serpentine beautiful, adorable, inspiring and more, but I’ve never called it a building stone. However, it can be.
Serpentine in its Sunday best is called verd antique. This closeup is from the iconic I. Magnin building at Broadway and 20th Street.
It resembles a particularly psychedelic marble — a translucent deep jade-green shot with intricate white veins. Petrologically, though, it is nothing like marble and a lot like soapstone. It consists of magnesium-based silicate minerals that are harder and more chemically robust than the calcite or dolomite that makes up marble.
Verd antique is all over downtown Oakland, usually as a subsidiary element at the sidewalk level. The building on 17th Street between Telegraph and Broadway has a particularly large expanse of it.
The Fox Theater building is another notable example. But in this post I want to draw attention to four buildings that do more with verd antique. The I. Magnin building (built 1930) naturally comes first, its entire first story richly faced with this stone.
The Foulkes Building at 419 15th Street (built 1924) has a high facade of verd antique with bronze decorations.
The Moyles-Kappenman building (built 1928), longtime home of Lobe & Velasco Jewelers, has a lovely front of verd antique on 1617 Broadway and an identical one at its other end on 1618 Telegraph.
Finally we have the otherwise undistinguished Wells Fargo building at 2040 Franklin Street, where the public-facing elements (entrances and ATM) are framed in verd antique.
The reason that all of these stones look the same is that for nearly a century a single quarry in Rochester, eastern Vermont, has been supplying the trade with Vermont Verde Antique(tm) stone. It is geologically special because it was squeezed two separate times, like twice-cooked fries, between colliding tectonic plates during the Paleozoic Era. As the supplier’s website puts it, it owes its origin to “highly sheared ultramafic rocks that have been rewelded and metasomatized by the process of serpentinization.” The lighter-colored “Cardiff Marble” serpentine from northern Maryland was once popular but is no longer produced. That stone is found in the White House’s Green Room, the National Archives rotunda and other places in Washington DC.
Verd antique gets its name from the Italian verde antico, “ancient green.” It was popular in Byzantine architecture. Oakland has a few pieces of European-style, brecciated verd antique to be seen here and there.
The stone industry considers verd antique a type of marble (it’s metamorphic and takes a polish) and follows ASTM standards for its manufacture, but verd antique is really its own beast.
You can’t do much with California serpentine except admire it. For an example, see the ecstatic response of an out-of-state geologist to San Francisco’s Marshall Beach exposures.