thumb|Beach pebble of variolitic pillow lava (varolite) from the Olympic Peninsula, Washington state thumb|right|Variolite pebble, Maguelone, Hérault, France. Variolites are mafic, igneous, and typically volcanic rocks, e.g. tholeiite, basalt or komatiite, that contain centimeter-scale spherical or globular structures, called varioles, in a fine-grained matrix. These structures are lighter colored than the host rock and typically range in diameter from 0.05mm to over 5 cm. In 1648, Aldrovandi created the term variolite for aphanitic or fine-grained igneous rocks containing varioles. The w
thumb|Beach pebble of variolitic pillow lava (varolite) from the Olympic Peninsula, Washington state thumb|right|Variolite pebble, Maguelone, Hérault, France. Variolites are mafic, igneous, and typically volcanic rocks, e.g. tholeiite, basalt or komatiite, that contain centimeter-scale spherical or globular structures, called varioles, in a fine-grained matrix. These structures are lighter colored than the host rock and typically range in diameter from 0.05mm to over 5 cm. In 1648, Aldrovandi created the term variolite for aphanitic or fine-grained igneous rocks containing varioles. The weathering of varioles often cause variolites to have a pock-marked appearance. In allusion to the pock-marked appearance of weathered surfaces of variolite, this term is derived from the Latin word, variola, for smallpox.
Varioles are millimeter- to centimeter-scale, light-colored, globular to spherical structures, that are conspicuously observable within aphanitic, mafic igneous rocks, such as basalt, komatiite, and tachylite, that comprise either pillow lavas, subaerial lava flows, or volcanic dykes. Typically, they are less resistant to weathering than the enclosing aphanitic rock and, as a result, form pock-marks on the weathered surfaces of mafic rocks.
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