Aragonite in the lower levels of Mercer Caverns, California
Mercer Caverns is a show cave located one mile north of Murphys in Calaveras CountyCalifornia. It is named after the gold prospector Walter J. Mercer who discovered the caves around 1885 and filed a claim. The caverns have a large number of speleothems, stalactites, and stalagmites. It is formed in a marble unit known as the Calaveras Formation. It also contains a large display of aragonite frostwork.  The standard tour of the cave descends 160 feet, 208 steps down and 232 up in a traverse between the natural and an artificial entrance. The cave was mapped in 1986 to a length of 3389 feet and a total depth of 192 feet. The map can be viewed on the cave's web site.
^Fife The Endless Adventure in the California Outback (2009), p. 191
^Mercer Caverns (Near Murphys, on Sheep Ranch Road, Calaveras County) Discovered by a gold prospector in 1885, who found no gold but did find human bones (four adults,one child, and one infant). — Mary Hill, in Geology of the Sierra Nevada: Revised Edition (2006), p. 159
^Rogers, Bruce; Legge, Charmaine (May–June 1995). "Mercer Caverns-History, exploration, and geology of a gold country classic". California Geology48 (3): 12–19.