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a paleotypal basaltic rock in which feldspar is represented by secondary albite. Spilites form as the result of underwater eruptions. Spilites have a microlithic or, less frquently, diabasic structure and consist of long, narrow microlites of albitized plagioclase with chlorite and ore minerals filling the spaces between the microlites. Together with keratophyres, spilites make up spilite-keratophyre formations of the geosynclinal stage of development of the mobile belts of the earth’s crust.