As far as "change moods" they function in much the same way as a little water foutain, or a USB-powered yapping dog toy, or pretty much anything else. If seeing a crystal changes your moods, then crystals have the power to change your mood.
For me, LOLCats have more mood changing properties than crystals.
Perhaps other individuals experience it in some other way. We have a sample size of one. I would bet that I wouldn't feel anything at all, and someone else might feel a cooling sensation. Maybe you feel whatever you most associate with "healing." Perhaps, in this case, the mark is most used to "heating pads" as a healing method as opposed to "ice packs."
Just an idea.