The behavior of ground water “frozen” in a rock

The name agate is given to any silica rock with color bands. This specimen is a geode—a mineral-filled cavity—but its layers are not the usual concentric rings. The cavity was filled by the slow accumulation of sediment from the bottom up. The layers are asymmetrical, with many bands showing sediment fining toward their tops. Thus we know that the specimen as oriented in the exhibit is right-side up!

The specimen in this exhibit is from the collection of the late Dr. Kenneth Ohme of Mitchell, Nebraska.