Category: Stories in Stone Blog

Slow Stone on Snowdon

Michael Welland of Through the Sandglass recently sent me this odd story about slate. A new visitor center has been atop Mount Snowdon, the tallest peak in Wales, at 1,085 meters. Judging from the photos in the article and accompanying web-based slide show, the building is quite handsome. It also replaces what that famed wordsmith Prince Charles called “the highest slum in Wales.” But what is more important is that in one of the world’s most famous regions for slate, the architect decided to use slate as a building material.

Photo of Hafod Eryri, the Welsh name for the building, from Snowdon Summit Blog

Slate quarrying was long Wales’ claim to fame and one of the most important industries in the country. Welsh slate was shipped around the world for use as gravestones, school slates, and most famously, for roofing. The men of the Welsh slate industry also traveled far. Poor working conditions, poor pay, strikes, and food shortages led to an exodus of Welsh workers to America in the 1840s. Their arrival jump started the nascent American slate industry and within a handful of years, slate from Pennsylvania, New York, Vermont, and Maine became the plastic of its day, a nearly ubiquitous material in the building trade.

Oddly, however, instead of using the 400-million-year old slate found on the sides of Snowdon, builders of the new structure imported their slate from Portugal. (Local granite, however, does clad the building.) I am sure that money was an issue but it seems odd to me that it wasn’t possible to find enough local slate to cover the roof of the building. Couldn’t the builders have simply gone around to abandoned quarries and just picked up some left over blocks of slate and made new roofing?

Stone has long been sent willy-nilly around the globe and as someone obsessed with seeing the wonderful stone used in the building trade, I shouldn’t complain, but sometimes I wonder if someone shouldn’t start a local stone movement, at least in a place such as Wales, where slate defined the country for centuries. I can see the taglines now: “Prevent the Reuniting of Gondwanaland; Don’t Ship Stone.” “Support Slow Stone; Use Only Regional Rock.” Okay, maybe I am living in a dream but I do think that in this world where we are trying to be more environmentally hip, that people should consider the global footprint of the stone they use. It can’t hurt to try.

Crab Orchard Stone

During a break at the AGU meeting in December, I was talking stone with Sid Perkins, who writes about geology for Science News. He told me about a rock with the wonderful name of Crab Orchard Stone. Eight months later, I am finally writing a bit about it.

Photograph courtesy of Sid Perkins, who retains the copyright.

Named for Crab Orchard, Tennessee, which in turn is named for groves of crabapple trees, the rock first reached national prominence in the 1920s. Prior to that, it had mostly gone into flagging, sills, and foundations. According to a 1961 report by the U.S. Bureau of Mines, large scale quarrying started around 1926, when architect Henry Hibbs sought stone for Southwestern University in Memphis. Several quarries still produce the stone, which in 2001 went into and onto the Country Music Hall of Fame, in Nashville.

Photograph courtesy of Sid Perkins, who retains the copyright.

The Crab Orchard is a beautiful sandstone ranging in color from tan to blue gray with shades of yellow, pink, purple, and brown. Adding to the appeal, the colors appear as lines and swirls, many of which form geometric patterns. Dense and fine-grained, it is “relatively impervious to moisture, and comparatively inert to acid or fumes encountered in manufacturing areas,” or so wrote the Bureau folks in 1961. They also observed that dirt and soot could be readily washed off. What more could one want?

Photograph courtesy of Sid Perkins, who retains the copyright.
The Crab Orchard stone is remarkably homogeneous, containing on average about 93% silica. It occurs in beds of uniform thickness, which allowed quarrymen to produced a single sheet that measured 111 feet long, 8 1/2 feet wide, and 3 inches thick. More often, the slabs used in buildings are smaller, and appear as treads, copings, garden furniture, wainscoting, memorials, and roofing.

Photograph courtesy of Sid Perkins, who retains the copyright.

Some controversy exists about deposition of the Crab Orchard stone. Some geologists propose that it occurred in braided streams and some that deposition took place in “back-barrier, tidal flat, and tidal channel or delta sub-environments within a barrier or marine-dominated deltaic system.” But all agree that deposition took place in the Pennsylvanian.

Photograph courtesy of Sid Perkins, who retains the copyright.

Recently, Sid was back in Crab Orchard and sent me a wonderful series of photographs of the stone. The above shots give a feel for the variety of colors and uses. If you are interested in using any of them, please contact me and I will pass your name on to Sid.