There's a lot of mystic background around jades
Some will feel cold to your touch and some will feel warm, despite the fact that they've both been exposed to room temperature for hours. I think you want the one that feels warm? My friend had a white jade necklace, it's half black: the longer he wears it, the whiter it becomes...weird stuff. Supposedly it protects you and merges with your life energy signature or something, you never want to take a dead persons jade...Don't know too much about it.