The mountain provides an example of the Great unconformity with the tilted Paleozoic Tapeats Sandstone underlain by Paleoproterozoic Vishnu Schist. An unconformity is a buried erosional or non-depositional surface separating two strata of different ages. We know when we find these that the sediment was not laid down in a continuous deposition. The range also boasts some of the oldest rock on the North American continent, at about two billion years old.
This spectacular specimen is in the collection of York Yuxi Wang. It is about 4-5cm long; 3-4cm wide.