Visitors to the Crater of Diamonds can find much more than diamonds here. One of the most common rocks found at the park is also one of the rarest to find beyond the borders of the crater. Lamproite is the volcanic material that erupted from the park’s diamond-bearing pipe around 100 million years ago. Four types of lamproite can be found at the park today, but not all are diamond-bearing. Knowing where each type of lamproite is found can provide insight into the park’s fascinating geological history.