<p>Olivine-basalt sand, Green Sand Beach, Puu Mahana Volcanic Cone, Hawaii Hotspot, central Pacific Basin.  Most sand grains here are ~1 to 1.5 millimeters in size.
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Weathering &amp; erosion of rocks at the Puu Mahana Volcanic Cone (tuff ring) has resulted in a concentration of olivine crystals at a beach near the southermost tip of the island of Hawaii.  This is modern marine beach sand from Green Sand Beach.  This is one of only two greenish, olivine-rich beaches in the world.  The green material is olivine sand ((Mg,Fe)2SiO4).  The dark gray material is basalt lithic sand.  The white material is biogenic aragonite sand (shell fragments).
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a>
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/jsjgeology/14849942188/">Olivine-basalt sand (marine beach sand, modern; Green Sand Beach, Puu Mahana Volcanic Cone, southern tip of Hawaii, central Pacific Ocean) 1</a>