To remove heat marks from quartzite, you can try the following steps:

1. Mix a small amount of baking soda and water to create a paste.

2. Apply the paste to the heat mark.

3. Let the paste sit for several minutes.

4. Use a soft-bristled brush to gently scrub the heat mark.

5. Rinse the area with water and dry it with a soft cloth.

If the heat mark is still visible, you may need to use a specialized quartzite cleaner or contact a professional for assistance. Its important to avoid using abrasive or acidic cleaners on quartzite, as they can cause damage to the surface.