Did you know there are black, white, gold, red and green beaches in Hawaii, along with the usual sand color. The green beaches are in an area on the Big Island, Hawaii.
"Puu Mahana, Green Sand Beach, is located in the Kau' district. It is primarily located on the slopes of Mauna Loa, the world's largest and most massive active volcano on the southwestern part of the island. To get to this beach, one must either use a four wheel drive or hike six miles from South Point, Ka Lae, the southern most tip of the United States.
The beach formed by the erosion and concentration of olivine crystals derived from the surrounding cone. The volcanic cone is Puu Mahana and it is a tuff ring (a type of volcano formed by the interaction of magma and shallow groundwater).
As ocean waves crashed against the coast they wore away at the cone and made a small bay along the coast. The waves also removed the lighter grains of sand (made of volcanic ash) leaving the denser olivine crystals behind to form the beach."