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An altered basalt containing albitized feldspar accompanied by low-temperature, hydrous crystallization products such as chlorite, calcite, and epidote.



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.

References in periodicals archive ?
* North of the Puerto Nuevo block the San Hipolito consists, in a hill some 3 km northeast of Puerto San Jose, of spilites and volcano-sedimentary strata; in a almost continuous strip that from a point about 2 km southwest of San Jose de Castro extends itself into the Ranchs of Santa Monica and San Miguel, reaches the Puerto Nuevo Canyon and continues in the Sierra de Puerto Nuevo, of spilites, pillow lavas, red radiolarites, sometimes coarse volcano-sedimentary strata, with both interbedded limestone and minor pink dolomite.
The fault scarp shows variable heights, the greatest relief (80-120 m) being observed upon slopes built up of spilites. Poorly-resistant and strongly weathered Permian tuffs have facilitated development of gently-sloping scarps.