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.

 

 

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