The occurrence of diamonds in Arkansas continues to intrigue geologists. About 100 million years ago a deep-source volcanic eruption occurred in this area, bringing material from the mantle rapidly up to the surface. The rising magma was rich in gases that expanded to thousands of times the volume that they occupied while under the enormous pressures at mantle depth. This rapid gas expansion produced an explosion as the magma approached the Earth’s surface. This explosion blasted a crater and blanketed the surrounding landscape with ejecta.

Within the ejecta were many fragments of mantle rock that were carried up to the surface with the rising magma. These fragments are known as “xenoliths.” They contained the diamonds.

Over time the ejecta was weathered, and a greenish soil formed above the crater. During the weathering process the least stable minerals were destroyed and the most stable minerals were concentrated in the soil. Diamonds are very resistant to weathering and were thus concentrated in the soil.