ساختار حبابی

thumb|A lithophysa from France thumb|A collection of lithophysae "thundereggs" A lithophysa (plural lithophysae, from Greek lithos "stone" + phusa "bubble") is a felsic volcanic rock with a spherulitic structure and interior cavity with concentric chambers. Its outer shape is spherical or lenticular. They vary in size from very small up to twelve feet in diameter depending on the age of the magma chamber. These rocks are usually found within obsidian or rhyolite lava flows. Lavas low in feldspar minerals may produce a version known as snowflake obsidian.