Reticulite is an extreme form of pumice in which the bubbles have coalesced, leaving only a tenuous reticular network of glassy lava behind in the interstitial spaces between the bubbles. Reticulite is formed only by very high fountains of basaltic lava that contain dissolved gasses such as water vapor and carbon dioxide. To form much reticulite, a lava fountain must be at least 1000 feet (300 m) high. Molten lava is shot into the air at such high velocity that gasses dissolved within it suddenl
Reticulite is formed when the lava is abruptly cooled, solidifying so rapidly that it does not allow the release of the gases contained in the bubbles after being ejected by a powerful lava source. The resulting material is a very fragile volcanic glass. This piece is from Kilauea volcano on Hawaii.