Shungite is said to be the "miracle stone" or "the stone of life", known for its incredible healing and protection properties. 
Potential Benefits:
EMF protection: Shungite is believed to neutralize the EMFs emitted by electronics like computers, phones, and Wi-Fi routers. A coaster is typically placed near these devices to absorb or deflect the radiation.
Energy cleansing: Many believe shungite absorbs negative energies from its environment. Using a coaster is thought to cleanse the energy of the space and objects placed upon it.
Grounding and stress relief: As a powerful grounding stone, shungite is said to promote emotional balance, reduce stress, and alleviate anxiety.
Enhancing drinks: Some users believe that placing a drink on a shungite coaster infuses the liquid with the stone's purifying and antioxidant properties. 
3 1/2 inch round coaster