“Lack of geological literacy is symptomatic of our general ignorance about the real world…”
(David Williams, naturalist)
It may seem a little strange, but I felt lucky to have lived a few years ago on a partially unpaved street. My old Queen Anne home sat on an old city lot that has one of the last vestiges of Seattle’s pioneer past, the bumpy, cobblestoned paving of the turn of the century, a rough hewn native granite. I fancy myself a “natural designer”, sure, and work a bit at it, but I hadn’t really thought of rock as being “native” until recently.
Most landscape designers often think of using natives, our minds usually going to the plant materials of our region, the myriad botanicals that we can specify and install in our glacial till soils, local plants that require minimal care and help us to restore habitat. Here in the Puget Sound, many landscape designers are familiar with local flora, but how many know their native stone? The source of your landscape stone impacts not only the cost, but the ecology and longevity of an outdoor project. Heavy and imported, out of state stone can have a significant eco-cost to split, shape and ship, much of it trucked from the Midwest or the east coast. Why not use local stone? So then, a quick primer on some of our resident stones*…
Index granite was originally quarried from the locale north of Seattle by that name. Originally sourced by John Soderburg, the founder of Swedish Hospital, Index granite is salt and pepper in texture, sometimes striated with veins of igneous basalt (or “heathens”, a rock quarry term). Its index granite that forms the beautiful cobbled paving on my street, little weathered after a century of use.
Chuckanut, an old Seattle building stone, a blend of feldspar, hornblende and quartz and may not be specified as a landscape stone, but it is important nonetheless. Quarried in Bellingham, Chuckanut is the foundation stone you see at the base of many of Pioneer Square’s old buildings.
Tenino sandstone was originally shipped from local rock yards near Olympia. Regular and consistently flat, Tenino provides a uniform grey toned earth hue with the benefit of a uniform walk surface as a flagstone and can also be found in ledgestone or thick paver forms.
Wilkeson stone is quarried from Eastern Washington, near Spokane. Wilkeson is lighter typically in color than Tenino and though relatively uniform, can be slightly rough surfaced on occasion. It’s available in a wide variety of split finishes, as a ledgestone and as an antique looking square paver.
Basalt and granite are most typically specified locally as wall stone and for other uses. These are used typically in paving, as wall rock in loose stacked, ledge-stone or as thin cut veneer, as accent stone or in water features. Granite can be a bit heavier, so you may get less rock per ton. For a paving project, dimensional or cut paving stone is usually quite a bit more spendy, as you are buying some wastage, the rock that is cut away as it is neatly split. Dimensional can also be a bit off-exact size as well, making the tight fit desired in fitted paved areas take a bit more time. Even a ¼” discrepancy can throw off an ashlar pattern pretty quickly. Random flagstone patterns are common, but here it’s important to plan for freeze/thaw stresses by avoiding weak imported sandstones and ensuring that you have a 1-1/2” minimal sandset thickness. This stone can be mortared as well. In this regard a ¼” thick material can be used, thereby offering more square footage per ton. This usually doesn’t translate into savings though, as a cement under-slab is also needed.
Stone is often denoted by “X-man” size or by tonnage. Think of a ton of bulk stone as a cone 3x3x2ft high. When specifying stone, I usually relate it to clients in this easy to follow fashion: “1-man” stone might typically be the size of a bowling ball, “2-man” the size of a large microwave oven, “3-man”, the size of a dishwasher and “4-man” the size of a washing machine. It’s important to note that the local rock purveyors will notch it up a bit by one size, reflecting the more accurate measurement of stone size,ie; “1-man” being what one man can lift with an eight foot prybar rather than the landscapers definition of what one man might lift. This effectively makes a “1-man” stone a “2-man” size in this regard, so do be careful when ordering. It’s easy to get confused, as local rock purveyors may offer the same stone under different “brand” names.
“Human consciousness arose but a minute before midnight on the geological clock. Yet we mayflies try to bend an ancient world to our purposes, ignorant perhaps of the messages buried in its long history. Let us hope that we are still in the early morning of our April day”. (Stephen Jay Gould)
*Reference: David Williams, The Street-Smart Naturalist, field notes from Seattle. Westwind Press, 2005. Marenakos.com, purveyor of stone in Preston, Washington.
(Photo: Placing the 'Palabra Stone' in Magnolia, 2010.)
