Alexander McAdam (1854?-1920s) was a minor character in Oakland’s history who left a highly visible mark in our cityscape. A Canadian farmboy who was orphaned at a young age, he came to California after apprenticing as a wheelwright, and after eight years he saved enough money to buy a farm “at the head of Thirteenth avenue,” according to a short biography by James Guinn in 1907. “He was successful in this occupation, but in the meantime had discovered a sandstone quarry on his property. Upon the sale of his farm he acquired considerable financial returns. Stone from it has been used in many of the largest buildings of Oakland, among them being the Unitarian Church, the last buildings of the deaf and dumb asylum, numerous retaining walls, and for many other purposes.”
This caught my eye because I have long thought that Oakland’s rocks were exclusively used as crushed stone. Yet here in the First Unitarian Church, ashlar blocks of genuine Oakland sandstone form the dignified cladding of this important cultural monument and civic institution, built in the early 1890s under the energetic leadership of a leading Progressive of his time, Rev. Charles Wendte.
Rev. Wendte oversaw the building project from his home across the street. The stone cladding was the costliest item in the project, and he singled it out in his memoirs: “Our employment of stone led to vexatious complications. Quarrymen were unable to deliver this material in sufficient quantities, workmen struck for higher pay in handling it. Contracts were broken or remade.”
I had to track down this stone somehow. The documentary clues are slim, and any signs of the quarry appear to be lost. But first, there is the stone itself.
It’s a fairly sound stone of an even consistency with a warm grayish-brown color and massive (i.e., absent) bedding. The block serving as a lintel over the doorway probably broke during the 1906 earthquake, when most of the cladding along Castro Street and the top of the tower collapsed. (The tower was rebuilt without any stone, a smart move.)
A closer look shows that the stone actually varies (although some of that may be substitute stone from another source, as Wendte’s wording suggests), and that a century of exposure has caused a fair amount of spalling. No wonder there were quality problems during construction.
A still closer look reveals it as a medium-grained wacke (“wacky”): a sandstone with grains no larger than a millimeter and a large component of minerals that are not quartz. The black grains are mostly biotite mica; without a microscope I’m limited in what more I can say.
It’s familiar to me. It’s not the Franciscan sandstone produced by the dozen or so quarries in and around Piedmont. I can rule that out categorically. It’s from the high hills on the far side of the Hayward fault.
All of this is consistent with the documentary evidence placing the source in Montclair. The “head of Thirteenth avenue” is where Park Boulevard, the former 13th Avenue in Brooklyn Township, meets Mountain Boulevard. It’s the intersection at the bottom of this excerpt from the 1897 topo map.
To orient (or disorient) you, here’s the same area today.
The “XII Report of the State Mineralogist,” published in 1894, said the following about McAdam’s quarry: “It is in Medos Cañon, back of Piedmont, and is a small quarry, producing sandstone for rubble and ashler [sic]. It is not worked regularly.” The official who wrote that description, a busy guy on a quick visit to cover the whole county, wrote down “Medos Cañon” when someone said “Medau’s canyon,” meaning the valley of present-day central Montclair where the dairy farm of John H. Medau once lay. I believe that if the site had been in Shepherd Canyon, his informant would have said so as that name was in wide use at the time.
All of this means that the quarry could have been a good exposure of the Redwood Canyon Formation, a wacke of Late Cretaceous age, that forms part of the east side of Montclair’s valley along the Hayward Fault. It’s the unit marked “Kr” on the geologic map, below. The lithological description of the unit, and the composition data from Jim Case’s 1963 Ph.D. thesis, are close enough to the stone in the church.
But also likely is the Shepard Creek Formation (Ksc) and even the Oakland Conglomerate (Ko), when you consider that the units are only subtly different, variable in composition and not well mapped despite the best efforts of competent geologists.
In any case, I had a good time visiting these rock units along the Montclair Railroad Trail the other day. There’s a lovely outcrop of the Redwood Canyon Formation above the trail along the route of the recently upgraded powerline, southwest of the word “grade” on the map. That warty weathered surface, reminiscent of the Incredible Hulk’s hide, is one of this unit’s distinctive features.
But the rock there’s not a good match.
Neither is the rock in the landslide at the upper end of the trail.
And just for good measure, here’s a chunk of sandstone from the Oakland Conglomerate. The material is coarser and wacke-er, but again under the 10X hand lens it’s not like the church’s stone.
Nowhere in this area, in many years of visits, have I seen a body of rock big enough and sound enough to support a quarry capable of producing ashlars — not on this side of the Hayward fault. The nearest quarry site is down Park Boulevard where the Zion Lutheran Church sits today, the former Heyland/Diamond Cañon/Bates & Borland quarry on the side of Dimond Canyon. But that produced crushed Franciscan sandstone, something quite unlike McAdam’s stone.
I can only conclude that McAdam found a lucky hillock on his farm and made the most of it, one that’s been obliterated during the waves of development since 1890. And the site of his farm is, as we say, poorly constrained. Even his life dates are fuzzy. But his accomplishments include making a profit from farming, acquiring a large home in Temescal, serving two terms on the City Council in the nineteen-oughts, and equipping an important building with a handsome exterior (despite the vexation he caused Rev. Wendte). I can’t confirm when he died or where he’s buried, so this building surely is his monument.
While I was researching this post, the papers covered a lovely story about how archeologists used advanced geochemistry to pin down the source of Stonehenge’s biggest stones, a peculiar sandstone known in Britain as sarsen. The New York Times version was my favorite writeup, and the hardcore details are in Science Advances in an open-access paper.
Oakland Geology 
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