VARIOLITE

Variolite is an old term that designates a basaltic rock consisting entirely of spherulites formed by radial aggregates of acicular crystals of feldspar (plagioclase) and pyroxene, with volcanic glass between the crystals.

Care must be taken not to confuse this structure with spherulites formed by the devitrification of volcanic glass.

Variolite 01: In PPL, with the lowest magnification objective (2.5x), radial aggregate of plagioclase and pyroxene in a variolite. The crystals are too fine to allow recognition of their optical properties. The dark volcanic glass between them contributes to masking what little remains.
Variolite 01: The same section as of the previous image, now in XPL. There are no features that help identify the minerals that make up the variolite.
In XPL, from the same sample of the two previous images, now seen with de objective of 20x.
In XPL, the same variolite of the three previous images, now seen with the objective of 40x.