Composite Quartz Kitchen Sinks. Quartz, the hardest constituent of granite constitutes around 80% of the raw material used in these sinks. The Quartz is molded with High Grade Acrylic Resin using a special computer controlled Polymerization Casting Process in Special High Grade Nickel Molds, to produce hardened composite material which is resistant to scratch, dent, stain, heat and cracks.