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Typical MineralsMinerals too small to identify (except phenocrysts). Composition will be from the top of Bowen's Reaction series (i.e. mafic) and we would expect Ca plagioclase, pyroxene, and perhaps some olivine. Note that these minerals are present in this specimen, just too small to see.
DescriptionA mafic igneous rock from the top of Bowen's Reaction Series. Typically dark colored, although weathered specimens can appear quite light, or reddish.
This vesicular or cellular specimen is full of holes produced when gas expanded as the lava was extruded to the surface. Vesicular varieties vary widely, and grade completely into scoria.
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Tectonic AssociationBasalt is one of the most common igneous rocks found. It is the major constituent of the upper layer of the ocean floors (usually as pillow lava), and hot spot volcanoes (such as the Hawaiian islands). Vesicular varieties such as this one are typically terrestrial, forming either on volcanic islands or on the continents.
Tectonic Cross Section - pdf version
|Last Update: 9/29/00||