Apache Tears

"Apache tears" originate from siliceous lava flows, lava domes or ash-flow tuffs, often in close association with or embedded in, gray perlite. The spherules occur as cores within perlite masses that typically exhibit concentrically curved, onion-skin fractures. Their formation is apparently related to differential cooling and differing alkali and water contents. Excessive water present during cooling and quenching of rhyolitic lava causes obsidian to hydrate (i.e., water entering the glass converts it to perlite). Where perlite is incompletely hydrated, fresh obsidian cores remain as pebbles of marekanite or Apache tears.