Variolite

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.

However, because several different mechanisms can produce these small-scale, light-colored, globular to spherical structures, a specific set of varioles may or may not be spherulites that are composed of radiating crystals of either plagioclase or pyroxene.

These analyses also found that their internal organization and geochemistry is incompatible with the hypothesis that they are quenched immiscible liquids, as has been suggested in the past by various authors.

[7][8] Finally, there is a group of spotted volcanic rocks formerly known to French petrographers as the variolites du Drac from the locality in which they are found in Parc National des Ecrins, France.

[13] Additional research has found them to be hydrothermally altered basalt volcanic rocks that contain amygdules filled with white calcite and other secondary minerals.