Quartz-fiber pressure shadow on fractured pebble, northwestern Arizona


I believe I collected this in Sue Beard’s thesis area in northwestern Arizona near the Cottonwood Cliffs.  This was back in ~1983-84.  This is one of my favorite rocks, …remarkable for being a pressure shadow you can hold in your hand, and use to discuss how pressure dissolution operates.

Age & Formation
Mazatzal Quartzite, Mesoproterozoic in age, ~1.5 Ga.