Not too many details as I can't recall much. 2005-ish(?) live-action American film where a boy finds glowing stones (not gems, but rocks with glowing portions) that hold some kind of power. The government, or some other kind of science officials, somehow get their hands on it, but the boy insists that "They're just.. rocks." I distinctly remember a scene where the little sister attempts to hold or touch the rocks whilst they are floating in their yard (maybe their power got activated?) and he yells something at her, probably to have her get back.
Sorry this isn't much info, will edit if I remember anything else.