PUU MAHANA VOLCANIC CONE
Weathering & 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 beach sand from Green Sand Beach (see photo).
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).
Olivine-basalt sand, Green Sand Beach, Puu Mahana Volcanic Cone, Hawaii
Hotspot, central Pacific Basin. Most sand grains here are ~1 to 1.5 mm in
size.
Olivine-basalt sand, Green Sand Beach, Puu Mahana Volcanic Cone, Hawaii
Hotspot, central Pacific Basin. Most sand grains here subangular to
angular. Microphotograph by Sara Beth Kopczynski.