Calcium deposits

A customer I have has some calcium deposits on thier unpolished granite pool deck. I’ve tried some rough steel wool, calcium deposit cleaner like lime away and vinegar. I can’t use anything super strong because it will pit the granite and make a mess of the situation. I bought a grinder and started on a small section as a test but that would take days. I’ve lightened it up a little where it was really light but haven’t found a way to take it all off. Any suggestions?

Is this that one customer Pete?

Give me a call back, i’m off the phone now lol