Secondary diamond sources are deposits that have been removed from the primary source (a kimberlite or lamproite pipe) by natural erosion and eventually deposited in riverbeds, along shorelines, in glaciers and on the ocean floor. They are also known as alluvial deposits. Although alluvial deposits account for only 10-15 percent of the world’s diamonds, they are generally higher-quality stones given that they retain more volume after polishing; they therefore command a higher price. The location of the diamond deposits determines the mining method that producers use (). Diamonds found deep in the earth are extracted through open-pit and underground.
