Basalts

Basalts: dark-colored, basic volcanic (effusive) rocks composed primarily of Calcic Plagioclase, Pyroxenes, and Olivine, occasionally with Amphiboles. They typically exhibit a microcrystalline texture and are rarely porphyritic, in which case they contain phenocrysts of Plagioclase, Pyroxenes, and Olivine. Basalts form extensive sheets and lava flows of varying sizes. Basaltic rocks alone account for approximately 90 % of all effusive rocks and lavas on Earth.

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