“Indian Dollars” are actually calcite pseudomorphs after twinned (trilling) crystals of aragonite. Width ~4 cm.
Google Earth© image of the Livermore area. Note the difference in topography along the North Livermore Fault. Farm land on the Paleozoic rocks change to the rugged topography of the Precambrian rocks.
The big change in geology happens in another mile and one-half where the highway crosses the North Livermore Fault! Travelers can easily notice the change from the Fountain arkose to the Precambrian (1.7 Ga event) gneiss and schist. This is a great place to observe a fault contact of major proportions (for a map see Braddock, W.A. and Connor, J.J., 1988).
Digital satellite image looking north at Virgina Dale Ring Complex, northern Larimer County, Colorado. Image by permission Dr. William Bowen.
Braddock, W.A., D. D. Wohlford, and J. J. Connor, 1988,
Geologic Map of the Livermore Quadrangle, Larimer
County, Colorado: U.S. Geological Survey Quadrangle
Eggler, D.H., 1968, Virginia Dale Precambrian Ring-dike
Complex, Colorado-Wyoming: Geological Society of America,