Purple Clear Skull Dead Island. This sculpture is cast in Polystone which is composed of polyurethane, resin, and mixed with powdered stone additives that give it added weight and a porcelain or "stone-like" feel. Polystone is very durable and delivers a cleaner, more substantial representation of an original sculpture than other common materials. Unicorn Studio uses polystone because it has an incredible ability to capture the most minute detail, making it unsurpassed in collectible manufacturing materials.