Try plain old white vinegar. Soak a cloth with it and set over the stain. Let sit for 2 or 3 hours wetting the cloth with more vinegar if it starts to dry.

Our calcium and lime deposits were way beyond anything vinegar could address. We found a product called Diamond Magic at a local hardware store. We had a thick calcium/lime layer on the shower doors. I wound up using the product with Grade 0000 steel wool on the glass. It took almost a month to get the doors clean. I keep a microfiber cloth near each sink and wipe off all water spots after use.

Norwex sells a wonderful natural De-scaler which removes lime, calcium and rust. www.NorwexLady.com

Here is a link that might be useful: Norwex

magic eraser!!!!

This is a Descaling Detergent

Lusto you question should have been from what type of material.

Giving out a product can damage different materials why you need to know what the surface is that is stained.

You guys should know that above anyone.