Molten lava erupted by volcanoes freezes very quickly, leaving holes where
gas bubbles used to be. These holes in the rock soak up fluids like a
sponge. A variety of minerals can settle out from the fluids and collect
along the bubble walls. You are looking at a cut through the edge of a
bubble in volcanic glass. This bubble has been completely filled up. A thin
layer of quartz crystals was deposited first, followed by the layer of
celadonite (orange). A piece of celadonite later broke off the wall and is
sealed in place by calcite which filled the rest of the bubble.