This spell allowed the caster to literally store a fireball within a valuable fire opal. To accomplish this the gemburst spell was cast upon the gem followed immediately by casting a fireball spell at the gem. The spell would fail if the fireball was not fast within one minute of casting gemburst.
Two methods existed for triggering the gemburst. The caster could select a command word at the time of the casting that would cause the gem to instantly explode. There was no range limit for this command word to work so long as the caster and gem were on the same plane. The other method involved the gem exploding when a certain set of circumstances was met. These could be as vague or specific as the caster wished. It should be noted that gemburst spells based upon a command word dissipated harmlessly if the caster died, but a gemburst spell based upon circumstances would continue to work after the caster's death.