SplendidSands

   South Point on the Big Island of Hawai‘i is the source of this green sand. These translucent green grains are olivine crystals. Near the sea’s edge, olivine erodes from a nearby lava flow and concentrates on the beach by wind and surf action. Olivine, heavier than most other sand grains, remains behinds when other grains are washed away by wave action. Olivine ranges from olive green to pale-yellow green depending on the proportions of iron and magnesium in its chemistry.

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   Pure olivine sand beaches are rare, but other Hawaii sands do contain some olivine grains.  Beyond Hawaii, olivine is found in igneous volcanic rocks that are associated with divergent plate boundaries or oceanic hot spots. We see it in sands from volcanic islands like the Galapagos, Canary Islands, Guam, some Alaska islands, Ascension Island near the Mid-Atlantic Ridge and elsewhere. Olivine is susceptible to weathering and is not found in well-weathered sands. If olivine is found in a sand, that location has volcanic past.

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   Peridot is the name for gem-quality olivine; it is the birthstone for August.