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Rust Stains On Sealed Granite?

Hi Tom,

What causes rust stains on a supposedly sealed granite shower base and sides or did the installer not impregnate seal it properly im guessing the later and you ?

Thanks, Rick

Hello Rick,

Lighter colored granite needs a heavy coat of sealant to prevent the water from absorbing into the stone but also consider the following. Often times after granite is properly sealed, users use harsh cleaning chemicals. Most of these cleaners will not harm the granite at all, but they will gradually dissolve the sealer and expose the granite to staining.

It sounds like you have another problem as well. Some granite colors contain mica which will rust. You can sometimes see this as a silver fleck in the granite. Even sealer will not prevent the eventual rust marks, usually in a circular pattern around the mica or iron mineral. The rust mark is deep but you could try ‘Iron Out’ found at your local home improvement store. Note, ‘Iron Out’ can etch granite a little so be sure to test it first. After you are done, apply a heavy coat of sealer.

Best wishes,
Tom Cordova

This entry was posted on Friday, December 29th, 2006 at 1:08 pm and is filed under Answers to Granite Questions..., Maintenance Help, Sealer Questions, Stain Problems. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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2 Questions Recently Posted:


  1. September 29th, 2008 at 1:45 pm

    I have new light colored granite that supposedly has been sealed well. A spoon with olive oil on it was left on the countertop overnight and a dark spot has appeared on the granite. I have never cleaned the granite with anything more than soap and water and the sealant appears to be intact. Is their anything I can do to remove or lessen the dark spot???


  2. January 14th, 2009 at 4:18 pm

    I have installed Bianca Romano granite in my kitchen and as a living room fireplace surround. It’s about 15 months old. I love the light coloring. Now, I am seeing more black flecks in the granite (in pieces in both rooms) than were there when the stone was installed. The installers have no real answer for me. They came out and determined it wasn’t mold on the stone. Is it possible that this is the “rust” to which you refer in some of your responses?

    I am frustrated because I expected my color to be constant. Now black is becoming a major feature of the granite.