ocean jasper

This variety of jasper, found only in Madagascar, is characterized by the presence of small spherical aggregates (spherulites or “orbs”), just a few mm in diameter, that derive from a process of alteration and silicification of former tuffs or rhyolites.
Spherulites are among he most interesting subjects I have worked with: they can be single or in clusters, made of fibrous or crystalline silica, with or without opaque-rich cores. Here are some examples.