Yellow Spots and Rust Spots on Stone

Yellow or brown marks, often referred to as "yellow spots," can appear on the surface of stones such as marble and granite. These spots may form from both internal changes in the stone and external pollution.

Causes of Yellow Spots:

• Marble: Yellow spots on marble are generally the result of internal changes in the stone after exposure to moisture. When marble absorbs dampness, it reacts chemically, which leads to the formation of these spots.
• Granite: In granite, the formation of yellow spots is primarily caused by the reaction of iron elements within the stone in a humid environment. The presence of moisture accelerates the change in iron, leading to discoloration.
• External Pollution: Yellow spots can also be caused by external factors such as rust pollution or dye contamination. These color-changing substances can settle on the stone surface, leaving behind noticeable yellow marks.
• Resin Adhesives: During stone installation, resin adhesives may seep into the surface, causing "oil seepage" which leads to the formation of yellow spots. This seepage can penetrate the stone and leave permanent marks.

Important Considerations:

1. Marble Yellow Spots: It is important to note that yellow spots on marble are generally not caused by rust. Instead, they are more likely to be the result of moisture exposure and internal chemical changes in the marble.
2. Granite Yellow Spots: When dealing with yellow spots on granite, it's essential to determine if the discoloration is caused by external rust contamination or if it is natural rust originating from the granite itself.
3. Humidity and Water: Humidity plays a significant role in the formation of yellow spots. Moisture can act as a catalyst for both internal and external causes of yellow spots, so it is important to assess the stone's exposure to water.

Distinguishing Between Marble and Granite Yellow Spots

Understanding the differences between marble and granite yellow spots is crucial for effective treatment and removal. Each type of stone requires a specific approach to address the spots, taking into account their formation mechanisms and the proper removal methods.