Lowry Mall Current Container Display
University of Missouri Department of Geological Sciences
Rock type: Amphibole Granite
Location: Knob Lick, MO
This igneous rock formed about 1470 million years ago when magma intruded a near-circular ring
fault at Butler Hill, Missouri. At that time, the local geology would have somewhat resembled
Yellowstone today, with a large caldera (a volcanic crater formed when the land surface sinks
into a magma chamber below) bounded by faults.
The minerals in this granite include quartz (glassy grey), feldspar (white and pink), and amphibole
(dark green), which indicates that the magma contained substantial amounts of dissolved water.
The granite crops out at an abandoned quarry, where the granite can be seen to contain
inclusions of the overlying rhyolite. It is thought that the granitic magma intruded into overlying
volcanic rocks that had previously been erupted from the same magma chamber.
Photo by Alan Whittington, MU Geology
MU Geology Department