It’s a great pleasure to work with good rock. I’ve nearly used up the excellent Laurel Mountain sandstone pallet I bought from the garden center. The photo shows one of the walls. I like the eclectic effect. To me, it shows well from all angles. I don’t know whether this sandstone really comes from Laurel Mountain or from some related quarry, or whether the stone company trucks it in from western Virginia, West Virginia, or Pennsylvania. This is a fairly common form of coal-country sandstone. It’s either Pennsylvanian or Mississippian in date and it is a coal-associated rock. This sandstone comes in flat, fairly uniform slabs that tend to break off square, rectangular, or as flat triangles. It’s easy to stack or to stand on end and piece together. Some pieces are stained with iron and some pieces have squiggles of carbon or thin bands of carbon and bog iron grit. It comes from the sandstone phase of the cyclothem, representing beach sand washed over a coal formation either because the sea level rose or because the plant-bearing muddy deltas that hosted the
coal forest subsided, or both.
coal forest subsided, or both.
http://www.britannica.com/EBchecked/topic/148194/cyclothem
The processes making these rocks were highly repetitious and are not too hard to understand. The muddy shale-bottomed swamps where the coal forests grew were a little above sea level. The ground was eroded clay and silt from inland, and iron was among the minerals dropping out in these layers. The coal seams and the shale beds can be anywhere from a few feet or a few tens of feet thick to mountainside-thick, depending on how long they were above the local sea level. When these beds sank or the sea rose, the result was a beach. The sandstone representing the beach phases of these cyclothems can also be anywhere from a few feet thick to hundreds of feet thick. The parts of these landscapes that were not muddy coal-tree deltas or sand beaches tend to be locally missing. Over time, lots of time, as the sea level fell again, or as the land rose, or both, the cycle would reverse itself with incursions of mud and plant debris until the delta overwhelmed the beach with brackish or fresh water and the coal forest reasserted itself, starting the next cycle of the cyclothem.
One can’t help enjoying the carbon seams in this sandstone. Floods or storm events would wash layers of iron-rich clay and masses of plant matter downstream onto the sand, to be buried, ultimately as a black streak in a white rock. Some of these bands are probably the debris of single events, one particular hurricane. Those forests, rivers and beaches, with their enormous dragonflies and bizarre amphibian wildlife, seem very very distant somehow and not easy to imagine, and yet it is just a fact that we can easily handle those beaches if we want to — stack them into walls. Somehow they speak of an unfathomable patience, a
tremendous leisure of sand and sea always ready to start over.
The processes making these rocks were highly repetitious and are not too hard to understand. The muddy shale-bottomed swamps where the coal forests grew were a little above sea level. The ground was eroded clay and silt from inland, and iron was among the minerals dropping out in these layers. The coal seams and the shale beds can be anywhere from a few feet or a few tens of feet thick to mountainside-thick, depending on how long they were above the local sea level. When these beds sank or the sea rose, the result was a beach. The sandstone representing the beach phases of these cyclothems can also be anywhere from a few feet thick to hundreds of feet thick. The parts of these landscapes that were not muddy coal-tree deltas or sand beaches tend to be locally missing. Over time, lots of time, as the sea level fell again, or as the land rose, or both, the cycle would reverse itself with incursions of mud and plant debris until the delta overwhelmed the beach with brackish or fresh water and the coal forest reasserted itself, starting the next cycle of the cyclothem.
One can’t help enjoying the carbon seams in this sandstone. Floods or storm events would wash layers of iron-rich clay and masses of plant matter downstream onto the sand, to be buried, ultimately as a black streak in a white rock. Some of these bands are probably the debris of single events, one particular hurricane. Those forests, rivers and beaches, with their enormous dragonflies and bizarre amphibian wildlife, seem very very distant somehow and not easy to imagine, and yet it is just a fact that we can easily handle those beaches if we want to — stack them into walls. Somehow they speak of an unfathomable patience, a
tremendous leisure of sand and sea always ready to start over.
Jorge Luis Borges’ “The Book of Sand” is one of my favorite stories. In this story a fictional Borges purchases at fabulous price a mystical book with an infinite number of pages—a frightening Lovecraftian artifact which despite its measureless length must rationally enclose an unimaginable middle page. In the end he hides it—from himself, as much as anyone. Strangely enough, there really is a book of sand, divided into folios of outwash and deposition. While the full scope of the real book of sand is utterly beyond the scale of human life and indeed beyond the scale of human existence as a species, we actually can turn some of the pages—they make great flowerbeds—although, like Borges’ narrator, we find ourselves limited to the parts we think we can understand and maybe invited to wonder what we are, after all, in terms of such gulfs of time.
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