The cleaning of gray quartzite surfaces

Cleaning quartzites is not as easy as it seems: you can use water with a little diluted denatured alcohol but this does not always lead to the desired results, especially in the presence of limestone or stubborn dirt.

For cleaning the surfaces of gray quartzite, the most suitable and effective products are “controlled action” buffered acids. The best product among the most used is phosphoric acid (H3PO4), capable of de-oxidizing and removing limescale from quartzite surfaces.
Phosphoric acid does not damage the stone and is less dangerous than muriatic acid, which by the way should never be used.

However, it is necessary to be very careful not to let the phosphoric acid come into contact with surrounding materials other than quartzite, such as aluminum for example: they can be irreparably damaged.
You must also be very careful not to touch the acid: when washing the quartzite it is recommended to use gloves, goggles and rubber boots as a precaution.
The first step in cleaning with buffered acid consists in wetting the stone and then intervening with phosphoric acid, which must be distributed evenly over the surface (with a broom if it is a floor) and rinsed with water after about 5 minutes.
To neutralize any residual acidity left with the treatment, you can use a basic product, which is also rinsed with water after the treatment.

For organic dirt, due to the classic macerated leaves or wood residues, washing with pure bleach and then rinsing with running water is sufficient.