DryStoneGarden

Three Rivers Flagstone

One of our clients calls Three Rivers flagstone “purple zebra,” which is a pretty accurate description. It always catches our clients’ eyes when they visit the stoneyard, though they often balk at the price, as it became really expensive a few years ago and is probably the most expensive flagstone commonly available in the Bay Area. It’s from one of the largest flagstone quarries in the United States, located up in the Sawtooth Mountains in Idaho. The quarry wanted to expand and the Bush administration, in their inimitable way, told them to go right ahead and not worry about doing an environmental impact study. An environmental group, the Western Watersheds Project, which owned a wildlife preserve adjacent to the quarry, then sued, and a judge agreed with the environmentalists that yes, U.S. law does require environmental impact studies, and temporarily shut down work at the quarry. Everyone settled out of court and the price then went up a couple of hundred dollars to around $750/ton.

I’ve seen the stone described as a type of quartz-sandstone and as argillite. Answers.com defines argillite as “an intermediate between shale and slate, that does not possess true slaty cleavage,” which sounds about right, except that I would add that Three Rivers is really hard and heavy. (Can I say that I prefer my stone with a bit more cleavage? It’s true. Cleavage is the tendency of stone to break cleanly.) The swirls of color in Three Rivers come from irregular mineral layers which look cool but make the stone inclined to break irregularly. The patio in the photo, for instance, has rougher, wider joints than I would do with a cleaner-breaking stone like a sandstone. To get tight joints with Three Rivers, you pretty much have to cut everything with a saw. We usually only use Three Rivers for stepping stones, paths, and small patios; it can look too busy when used for larger areas.

Quarriesandbeyond.org has links to info about the Three Rivers quarry on their list of quarries in Idaho.

Three Rivers Flagstone Patio

Arizona peach flagstone patio

Building patios is hard on the body. Too much bending, awkward lifting, and the wide spread of the stone amplifies the weight of the stone; building walls is much easier on your back. I feel like I could build walls until I’m sixty, but there must be a limited number of patios in my back. So a couple of months back I made a decision to build only 40 more flagstone patios in my life. That number is just as subjective as it sounds. (more…)

Sunset should have a description for Arizona flagstone: drought-tolerant, best in full sun, tolerates some shade, longer lived in well-draining soils, short-lived in zones that get hard frosts.

It’s from the Southwest, so it likes Southwestern conditions, same as the plants. To give it the drainage, it’s best to lay the stone in decomposed granite and gravel, but at our house, a rental, we wanted to keep things cheap, so we laid our flagstone in dirt, and it has done okay for us. It settled more unevenly than it would in DG, several of the thinner flagstones cracked, and the stone didn’t hold its color, but the graying, mossy flagstone patio fits into the rustic aesthetic of our yard so we’re happy enough. Arizona flagstone tolerates shade and clay soil, it just doesn’t thrive in it.

We planted a few different groundcovers in the joints of our patio. The baby’s tears is looking the best these days, during the winter rains. It used to dry out during the summer, but this year we had some pots near it, so it got the water that drained out the bottom of the pots, and managed to stay green all year. It’s probably our favorite groundcover for damp, mossy areas.

– Addendum –

Arizona Flagstone Patio

Here’s a photo of the patio in May. The baby’s tears is in the back behind the heuchera flowers.