The crystals or sediment left behind on fixtures, white surfaces, and pots after water evaporates are calcium and magnesium carbonates. These are naturally occurring minerals and do not pose a health hazard. These deposits may 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. Dishwasher deposits can be minimized by using a commercial conditioner, by using liquid detergents and by using the air-dry instead of the power-dry setting on your dishwasher, which bakes the carbonates onto glassware.