Johnson Granite Porphyry is found in Tuolumne Meadows, Yosemite National Park.
[1] Its area is estimated at 1,100 square kilometres (420 sq mi), the exposed area covering roughly 40 square kilometres (15 sq mi).
[4][5] The innermost, most felsic part of the Tuolumne Batholith is the Johnson Granite Porphyry.
Completely surrounding it is the much larger body of Cathedral Peak granite.
[1] Field observations and magnetic fabrics suggest an extrusive event, that is, Johnson Granite Porphyry may record possible volcanism.