Tag Archives: concretions


Concretions form in a slurry of mud or sand, when a bit of organic material starts a chemical reaction that alters the minerals in the surrounding slush. Most often it forms a sphere, but sometimes all kinds of weird shapes.
Eventually the reaction stops and the slurry hardens into stone. Aeons later, when the stone is exposed, the concretions—usually harder than the surrounding rock—weather out.
As in the top photo, if you break the concretion open you may see traces of the original reaction. Pretty!
Boots Cuba bflyconcr
Boots SnLuis marbles
Boots SnLuis wheel
Boots SnLuis planets


Sheepherders monumentRed Mesa. The redness of the rock, and of the plants as well. Even the grass is red at the base. Perhaps that’s just the color it is—it might be Little Bluestem, such a contradictory name—or maybe it picks up the iron in the soil. Tracts of red sandstone are covered—covered—with knobby, black, marble-size concretions.

At the edge of the rugged canyon is a sheepherder’s monument, a two-legged stack of red sandstone reminiscent of an Inuit inuksuk. Old cairns mark the sheep trail down into the barranca.

Three big red potsherds lie where a pot was dropped, hundreds of years ago.


Face Down

SlotCanyonDB124The day began with mottled clouds that later burned off. No friendly sand to walk in, just acrid mud dust, with now and then a stiff, dried place where a cow had pissed. We hiked down terrifying deep arroyos whose walls, scored by mud-laden runnels, were poised to collapse.

Mudstone concretions: eyeballs and entrails lay in drifts on the yellow-red dirt. We came across two half-buried spheres, both about twelve feet in diameter, like the backs of two huge skulls: Baba Yaga and her daughter.