Complex Stories

Banded Agate/Jasper, Olympic Peninsula

When I studied geology at the University of Washington, my favorite class was one called "Structure" in which we tried to piece together the sequence of events that have altered rocks and landscapes by reading the stories within them. If one continuous layer in a sedimentary rock is offset along a plane, for example, you could infer that a fault had shifted AFTER the deposition of the layers. (see the faulted jasper in my August 25 post). Sometimes, however, multiple events can overlap, creating a very confusing picture.

That's what's happening with this rock, which I found among beach cobbles on the Pacific Coast of the Olympic Peninsula. I'll call it an agate/jasper (or "jaspagate" as I've seen it written elsewhere) which is simply another name for a rock that has features of both: the transparency of agate and the opacity of jasper.  Whatever you want to call it, this small pebble seems to tell the story of fracture and fill: an existing red jasper was fractured, possibly several times, and injected with quartz solution - both clear and vivid red. How did this happen?  I have no idea, but whatever the story, its this complexity that helps create this handsome visual pattern, one with tantalizing hints of the paintings of Jackson Pollock.