Can you use Purple Mat with clothes on or does it require direct contact with the skin?

The mat is multifunctional. For FIR heat, crystal rays, negative ions, pulsed magnetism (PEMF) you may use the mat with clothes or without as per your choice. Some natural materials like cotton or bamboo are preferable. There are also protective waterproof cover and a 3-d air mesh pad in the set to cushion the mat and make it more comfortable during the first time while your body gets used to stones pressure. Later they can be removed while sessions and only the waterproof cover put on the mat for protection and storage.

But this mat has also red light LEDs photon function. You may use in the clothes and with protectors on the mat but the most past of visible red light will be blocked. So if you would like to have full benefits from this function, it may be reasonable to use the mat bare. I think it would be better to do when you get used to stones pressure and can stay on the mat at least for 20 minutes without cushioning protectors or clothes.