Oakland building stones: Lime stones

There isn’t a good word for the full variety of carbonate building stones — limestone, dolomite, marble, marlstone and travertine. Although I like the word limerock, it apparently doesn’t really exist. In any case, these rocks aren’t very common in Oakland’s buildings, the way they are in, say, Washington DC (all of those memorials, and the Pentagon too).

Part of the reason is that limestone/marble is uncommon in California, and here it’s more valuable as an industrial material than as dimension stone. For limestone, think Indiana and Wisconsin. For marble, think Alabama, Texas and Colorado.

Panels of fossiliferous limestone decorate a building at 9th and Clay.

fossilif-ls-panels

Take a closer look at all the fossils.

fossilif-ls-detail

A builder might call this marble because it takes a polish, but in my language geologists call it marble only if the rock has been metamorphosed, and that would erase all of these fossils.

Its warm color indicates a certain content of clay minerals as well as calcium carbonate minerals (calcite or aragonite). If clay is present in amounts comparable to the carbonates, the stone is referred to as marl or marlstone. The Torrey Pines Bank building, on Webster Street, uses a striking combination of buff and black marlstone. A small building can pull off this look.

marl-bank

The light stone is quarry-faced. The dark stone is fully dressed and then bush-hammer finished to lighten its color.

marl-corner

This stuff has a few fossils in it, too.

marl-fossils

Limestone is a sedimentary rock that forms in warm, shallow seas where sea life, most of it microscopic, takes calcium carbonate out of solution to build its shells. These limy shells pile up and are consolidated into stone at low temperatures and gentle conditions.

You’ll see this environment in the Bahamas, for instance, but the current geological age is not a limestone-building time because the seas are so low. For most of geologic time the low parts of the continents have been warm, shallow seas. Hence the huge limestone beds of Indiana and the rest of the Midwest.

Then there’s travertine. It’s not marble in my language, but it takes a polish so it’s industrial marble. Here it is next door to the Torrey Pines Bank.

travertine-panel

A closeup shows its weird — I mean, attractive character, full of pore spaces and irregular layers.

travertine-detail

It seems like it might be fragile, but it’s very strong. The ancient Romans loved it, and Italy supplies most of the world today. The Getty Center down in L.A. is a veritable Disneyland of travertine.

travertine-getty

Mountain View Cemetery uses a lot of it too.

travertine-mvc

Travertine grows in freshwater marshes, fed by springs of groundwater that’s full of dissolved limestone. It’s actually a renewable resource.

Marble, real marble, metamorphosed and recrystallized limestone, is a common accent and interior stone in Oakland. I like this staircase in City Hall, which pleasingly contrasts detailed tilework against the warmth and translucency of fine marble. The stairs are marble too.

marble-cityhall

“What about dolomite?” you ask. “You mentioned dolomite up there.” The mineral dolomite, magnesium-calcium carbonate, can be present in limestone and marble without affecting the names we give those stones. Pure dolomite rock, or dolostone, is pretty unusual as a dimension stone. But Oakland has a spectacular example of dolomite aggregate used as the facing of the Kaiser Center, which I featured here a few months ago.

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3 Responses to “Oakland building stones: Lime stones”

  1. Jeffrey Allen Says:

    Speaking of stones, can anybody shed some light on the significance of the pylons at either end of Lake Merritt, square prisms of alternating thick sandstone and thin limestone blocks with the number “1800” etched into the top of each pylon? I’ve been trying to find someone at Parks and Rec who knows, or any reference at all, but have been unsuccessful. They are laid out in a meandering path that suggests they might mark a former natural boundary (water’s edge?), but I can’t verify that.

  2. Andrew Says:

    Those mark the original pre-settlement shore of Lake Merritt, or San Antonio Slough as it was once known.

  3. Jeffrey Allen Says:

    Thank you so much! Does 1800 refer to the approximate date? I found a study that someone had done to identify the Bay shore in 1800, perhaps these are connected with that study(?) There must have been some sort of dedication ceremony when these were installed, but I haven’t been able to find any news accounts or records associated with the lake improvement bond measure, which presumably funded the monuments. Any ideas where to look?

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