When natural crystals grow from a magma, they often trap parcels of the melt as inclusions. This image is an optical microphotograph (10x magnification) of a green Hawaiian olivine crystal containing nearly spherical melt inclusions, one of which is in focus in the foreground. The long axis of the inclusion is ~120 microns. When the crystal is cooled quickly the trapped melt is quenched to a glass, as seen here. Magma often contains dissolved volatiles (H2O, CO2) and when depressurized the gases exsolve to form a vapor bubble, which is the smaller spherical feature within the melt inclusion. The faint spindles are Mg-Fe silicate crystallites that nucleated on the inclusion wall, probably during the eruption of the lava. The brilliant green hue is the natural color of Mg-rich Hawaiian olivine.