SRD:Elemental Gem

Elemental Gem: This gem contains a conjuration spell attuned to a specific Elemental Plane (Air, Earth, Fire, or Water).

When the gem is crushed, smashed, or broken (a standard action), a Large elemental appears as if summoned by a summon nature’s ally spell. The elemental is under the control of the creature that broke the gem.

The coloration of the gem varies with the type of elemental it summons. Air elemental gems are transparent, earth elemental gems are light brown, fire elemental gems are reddish orange, and water elemental gems are blue-green.

Moderate conjuration; CL 11th; Craft Wondrous Item, summon nature’s ally V; Price 2,250 gp.