Lustro Italiano > Natural Stone Care > Caring For Granite > Where Rust Comes From

Where Does Granite Rust Come From?

We occasionally get phones calls or emails from customers asking for products that can remove stains from granite or other kinds of stone. As a general rule, we have the customer send in a photo of the stain so a technician can identify the kind of stain the customer has and make a recommendation on how to treat it. When it comes to rust though, the answers vary regarding how to treat the stain. In this article we will share an experience that highlights the answer to the question, "where does granite rust come from?" We will also look at what you can do to protect your granite stone surfaces from rust; from many origins.

Customer Stain Inquiry Appears to Be Rust

Not long ago, we had a customer reach out to us via email. He was asking about a specific stain he was trying to remove from granite. He sent in a photo to get help from a technician on how to treat this unsightly blemish. Here is a copy of the customer's question:


I have a small stain on my granite and was trying to determine what product I would require to purchase from you. Here is a pic of the stain

<customer name protected>

He included a photo of the stain and a technician took a look at the image. The technician replied with the following:

<customer name protected>,

Thank you for your interest in Lustro Italiano products! This appears to be a rust stain from iron ore inside the stone unless you know of something else causing the stain? If this is what it is from, it can be a challenging stain to remove and then prevent form coming back again. My suggestion is to use the Lustro Italiano Rust Remover Powder and in the directions where it says to add water, instead add the Tenax Liquid Rust Remover to create your poultice to draw out the rust stain. Like I said, this is a challenging stain to remove and so this process may need to be done multiple times to remove or minimize the stain. See the links below for more information and purchasing of these two products...

After the stain is removed to your satisfaction, I would then highly suggest sealing the granite with the Lustro Italiano Ultra Premium Stone Sealer. This will be important in trying to keep the rust stain from re-appearing as the sealer will help keep any moisture out of the stone and help prevent the rust from coming out again. For more information on the sealer, see the link below...

And lastly, I always suggest that people use the Lustro Italiano Stone Cleaner and Polish Kit to keep their countertops looking amazing for years to come. The Stone Cleaner is an excellent daily cleaner that is safe for your stone and as a side benefit, it is also an excellent stainless steel cleaner as well! And the Stone Polish is used similar to how you would use Pledge on wood as you can use it when you want add a little extra luster or "pop" to your countertops. It also has some sealer in with it so every time you use it your adding a little sealer which will help make your sealer last longer!

Let me know if I can help you any further!

Thank you!

Rust Inside Stone

Rust Can Come From Inside Granite

As you can infer from the response of the technician, it is possible for rust to develop inside a granite slab. If this happens, the stain can be quite challenging to remove. This is not the most common type of rust stain found on granite surfaces, but it is one of the possibilities. And occasionally, we get customers that send in photos of a stain forming inside of granite. How does this happen? To answer that, we need to look at what causes rust.

What Causes Rust?

To find out what causes rust in general, all one has to do is run a quick Google search on the question "what causes rust?" When you do, you will most likely get back an explanation similar to the following:

Rust occurs when Iron, Oxygen, and moisture combine. When these three ingredients are combined, oxidation happens and produces a chemical reaction forming Iron Oxide or Ferric Oxide (a.k.a. Rust).

With that general recipe for making rust, we can begin our discussion of rust as it relates to granite.

Rust and Natural Granite

Now that we have covered how rust forms, it really doesn't take much to determine where granite rust comes from. The three ingredients needed to make rust are readily available in most environments. In fact, two of the three, water and oxygen, are pretty much everywhere.

So, to figure out how a particular rust stain developed, all one has to do is determine which iron source came in contact with wet granite in the presence of regular old air - since air has oxygen in it. As the technician explained to our customer, granite sometimes contains iron. And, in this case, the iron from inside the rock itself was meeting with moisture and oxygen to create the reaction explained above.

Rust that originates from within granite can be the most difficult to remove, yet with determination and good old fashioned "elbow grease" nearly all rust stains can be treated. Even if they cannot be removed completely, they can very often be lightened greatly (as the technician indicated in the response above).

The stubborn old internal rust stains that can develop in granite is not the only source though. Some other substances that contain iron can create rust stains on granite and other types of stone around your home. Let's look at these now.

Metal Causes Granite Rust

Perhaps the most frequent cause of granite rust is a metal substance that remains in contact with a piece of granite over a period of time. When this situation occurs in a moist or wet environment, rusty granite is inevitable. The three necessary parts are there: Water, Oxygen (in the air), and Iron (in the metal). This will most likely only be a surface rust stain and can usually be removed easier than other types of rust stains.

All sorts of household items can become the culprit. Here are some items that could be the vehicle for rust to develop on your granite:

  • Razor Blade
  • Metal Handled Fly Swatter
  • Nails
  • Metal Handled Spray Nozzle for a Garden Hose
  • Hose Clamps
  • Key Rings
  • Paper Clips

Virtually any metal object that might get overlooked can become the third ingredient for the rust recipe we mentioned earlier. Yet, if this is the cause, the rust is most likely going to be easier to remove than it would if it were caused by other sources.

Granite Rust From An Unlikely Source

In addition to the rust stains that come from within granite and the ones that can form on its surface through contact with metal, there is another common type. This cause of granite rust can be somewhat tricky to detect because of the iron source. What is it? Lawn fertilizer that contains iron can be the way in which your stone - not just granite - comes into contact with the oxygen and water to generate rust.

In this case the iron is in a form that allows it to be easily absorbed into the stone with the water. So this cause of granite rust can be more difficult to remove than the metal on the surface but easier to remove than the stains that form from inside the granite.

Depending on which type of rust stain you have on your granite (or other stone), you will need to attack it differently. However, as a general rule, rust stains can be treated if you are willing to take the fight to them. And after you treat the stain, protecting your stone from future stains depends on removing one of the three necessary ingredients that cause the reaction that produces the stain.