Use the Amazing Power of Baking Soda in the Bathroom
Truly a universal cleaning agent, baking soda is a safe and effective way to clean bathroom sinks made of any material.  Not only will the sink sparkle, but surrounding tile countertops will gleam from a gentle scrubbing of baking soda on a damp sponge.  Use a soft bristle brush (old toothbrushes are perfect) to get into grout lines.