What is the white residue I sometimes find on cookware and the shower?

White residue is commonly found on kitchenware and glass shower doors as the result of dissolved minerals found in water, such as calcium, magnesium, and silica. These are naturally occurring minerals and do not pose a risk to human health, but can build up on surfaces over time. These deposits may also appear green, blue, or brown, having been colored by tiny amounts of the metals found in your water pipes. Carbonate deposits can be dissolved with white vinegar. Also, commercial products are available to remove white residue caused by minerals in the water.