Portland Building Stones for GSA

With GSA just around the corner, I thought I would highlight some of the local building stones in Portland. Most of what I will be discussing is across the river, in the downtown part of the city. The area is a short walk from the convention center and perhaps might offer a welcome diversion when you get glassy eyed during a talk or two.

I will start with some of the local stones used in buildings. One of the best showcases is the First Congregation Church on the southwest corner of Madison and Park Avenue. Started in 1880 but not completed till 1895, the church formerly had three towers, but only the 185-foot-tall one remains. The base is made of black Oregon basalt, from one of the many great Columbia Plateau basalt flows. These flood basalts, which erupted primarily from 17 mya to 15 mya, are the second most voluminous on the planet. They cover much of the Columbia Plateau, and flowed down the Columbia River basin to Portland. Outcrops of the basalt occur throughout Portland.

The First Congregational Church (from Trey Rice’s Flickr account)

Nestled around the basalt, and checkerboarded with it on the south wall, is the Tenino sandstone, from quarries 20 miles south of Olympia, Washington. Streams washing across a pre-Cascades landscape deposited the sands into deltas that poured into the Pacific Ocean. Fossils found in other parts of the region show that the climate was sub-tropical with abundant growth of palms. The Tenino deposits have been dated at around 50mya. Gray-greenish in color, they provide a nice contrast to the black basalt.

Curiously, basalt cobbles are also used in a rubble wall on the block surrounded by Fourth and Fifth and Market and Mill, but the stones are not from Oregon. Instead, they are Belgian basalt used as ballast in ships that offloaded cargo at the base of Clay Street. This wall originally encased a catholic church and the parishioners wheelbarrowed the stones up from the waterfront for their building project. As Ralph Mason notes in his splendid guide to Portland’s stone (Oregon Geology Vol. 47. No. 11, which provided most of the information for this article), the devout could have gotten basalt from a nearby cliff “which is several thousand miles closer and a downhill haul.” They say that suffering builds character, and churches.

I will end with a boring building architecturally but a fascinating one geologically. Two types of widely used stone clad the building that takes up the block between Jefferson and Columbia and 6th and Broadway. What makes it interesting is the great unconformity between the base and the upper floors. The 3.5 bya Morton gneiss in all its gaudy glory covers the base and atop it sits the 330 mya Salem Limestone, both stones of which I have blogged about before.

Oregonian building (from Wikipedia)

I have focused only on the older buildings in Portland. Many new structures showcase stone from around the world. As noted at the beginning, I highly recommend a tour. Mason also wrote an earlier tour of Portland buildings for The Ore Bin, volume 27, no. 4, April 1965.

Bluestone and "a thousan’ rattlesnakes"

The most famous building stone in New York after brownstone is another sandstone known by its color: bluestone. The term generally refers to flagstones quarried in the Hudson River Valley in central and south New York, as well as in northern Pennsylvania. What made it so popular was the sandstone’s ability to be split into slabs of consistent thickness, which could then be used most famously for sidewalks.

Classic bluestone sidewalk, on a street of classic brownstones in Brooklyn

Beginning in the early-1800s, numerous bluestone quarries opened to provide stone for New York city. According to the Jan 17, 1872 New York Times, one “Uncle Steve” Griffin, a “noted character,” found one of the earlier quarries while out on a rattlesnake smoking expedition near Westbrookville. The area was noted for rattlesnake dens and a local pastime was to “kill the venomous inmates [by] prying and smoking them out of their places of resort.”

Antique bluestone paving for sale. (From Monterey Masonry in western Massachusetts)

Griffin had located a den and inserted his crowbar when he was “astonished by the splitting of a thin, smooth slab.” The Times added “[Uncle Steve] did not attach any importance to his discovery, merely remarking when he returned home that he had “killed more’n a thousan’ rattlesnakes, and had buried ‘em under a patent grave-stone he’d found there.” He subsequently exhibited his “patent grave-stone” to others, who at once pronounced it a blue-stone quarry.” The quarry, however, wasn’t developed for 35 years, when in 1865, six barge loads were shipped to market.

The bluestone flagging went into curbs, caps, sills, and steps—called “edge stuff”—as well as street pavement. Bluestones got their name from the blue color, though the sandstone ranges from gray to green to lilac. The quantity and type of iron controls the colors with chlorite imparting green and hematite bestowing lilac. An absence of hematite, along with unaltered iron minerals generates the famous blues.

Bluestone has also been used to describe bluish limestone, particularly in the Shenandoah Valley. Good examples of this stone are found on the James Madison University Campus. Archaeologists working at Stonehenge also refer to the igneous rocks there, such as diabase and rhyolite, as bluestone.

The majority of the quarries are in Devonian rocks. In New York the rock is the Upper Walton Formation of the West Falls Group and in Pennsylvania, this group is equivalent to the New Milford Formation. The sands were deposited in a classic delta complex, of shoreline and non-marine alluvial plains dotted with lagoons and tidal flats. Quartz is the dominant mineral with a quartz cement.

One of the best single sources on the history and geology of bluestone is a report by James Albanese and William Kelly. It was published for the New York State Geological Association meeting in 1991 and contains most of the pertinent details about the rock that I used. (It can be found in the NY Geo Assn Guidebook, vol. 63, pages 191-203.)

Although the hey-day of bluestone sidewalks passed long ago, many still recognize the beauty of the stone. For example, Marbletown, a community in the Hudson Valley, recently received $3 million in federal stimulus money to build a 3/4-mile bluestone sidewalk. Now, who says that the government does not spend our money wisely?