Labhraín
Do you think that crystals or any stone for that matter, have to touch your skin to be effective?
Not at all.
(Bit longer than ThinBuddha's reply.)
My feelings is that if 'we' are within their aura, there is benefit.
NB, completely my own thoughts and I cite no words by people far more knowledgable.
As I type, I have a largish Citrine crystal near me, and my wallet. Money-wise I have had financial improvements since bringing this crystal to my home. I got the crystal for those properties.... I feel it is happening.
It's how you or I perceive the crystal, and its usage, that matters, imho.
Blessings
GMB