Basalt
Written by Boss Tambang Tuesday, 01 December 2009 23:19
Basalt is a dark, heavy, iron-rich and silica-poor volcanic rock that makes up most of the world’s oceanic crust. It represents the Earth’s upper mantle or, in this case, a hotspot magma that arises from deeper in the mantle. This specimen is a broken cobble picked up at Cape Kumukahi on the island of Hawaii, where it was erupted from Kilauea in 1960. Bubbles of carbon dioxide and water vapor formed and expanded in the molten rock as it approached the surface. During its long period of storage beneath the volcano, green grains of olivine came out of solution as well. So the bubbles, or vesicles, and the grains represent two different events in the history of this basalt.
It is supposed to be bad luck to carry off a piece of Hawaiian lava if Pele is not paid proper respect first. The Hawaiian Volcano Observatory receives rocks from repentant mainlanders all the time. This specimen was properly collected and may be viewed in safety.
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