Volcanic litharenite, Black Sand Beach, Big Island, Hawaii
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Black Sand Beach |
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Macroscopic view, line in |
Location:
South shore of Big Island, Hawaii, Black Sand Beach
Provenance:
Volcanic sand of recent basaltic lava
Composition:
Dominantly light green volcanic glass, isotropic in polarized light. A few colourful clinopyroxen crystals (maybe olivine as well ?) and a few microlithic VRFs
Petrographic thin section:
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Basaltic VRFs |
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Bright field |
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Dark field |
Texture:
A coarse-grained, moderately to poorly sorted, extremely angular volcanic sand of recent basaltic lava. The extreme angularity and the preservation of many partial bubble outlines is unusual in sands but highly diagnostic in the interpretation in sandstone provenance. Medium to coarse sand (250 to 1250 μm)
Sample number |
Collector |
Date of sampling |
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heubeck0085 |
Christoph Heubeck, Institut für Geologische Wissenschaften, FU Berlin |
1991 |
Comments:
Along Hawaii's south coast, basaltic lava, up to 1100 deg C hot, is shock-cooled upon contact with the sea water. Glassy beads and highly porous basaltic "spatter" form which are quickly ground up into shards by shoreline surf and swash. The black beach becomes extremely hot under the morning sun
