Minimalist design. Generous function. MTI's Petra lavatory sink models are constructed using MTI's proprietary Engineered Solid Stone, a mixture of ground natural minerals and binding agents that are liquified, poured and then hardened. Non-porous, stain-resistant, mold and mildew-resistant. Easy to clean, the Petra Double lavatory sink will continue to look brand new with minimal maintenance. The Petra Double lavatory sink is designed to mimic the lines of the Petra bath tub.