Only three miles outside Hana, there is a beach area known as Waianapanapa. The swimming is dangerous here during heavy surf because the bottom drops off quickly, but on a calm day it is nice. The sand is black at Pailoa Bay, a sharp indentation in the coast beyond Hana airport. Water-worn pebbles and cobbles clatter as they roll back and forth with the movement of the waves. Now black sand beaches are rare anywhere in the world.
Most beaches are of light colored sand.
In the tropics, that usually means that the sand is pulverized coral. Some form when hot lava flows enter the ocean, causing a steam explosion that blows the molten material into millions of glassy fragments. You will find a very few beaches like that on the Big Island of Hawaii. These beaches are short lived as there is no reliable source of new material to replace what the ocean and the wind carry away. The chances of another flow occurring in the exact same place and in the same way are very remote.