It is impossible to apply water-repellent when the floor is completely dried. It is strongly advised to test any product on a sample before using it.
Natural stone materials can be cleaned with a mopping cloth and water. Some specific soap can be used or Marseille soap: 30 g of soap for 10 L of water.
Never use aggressive products like bleach, detergents, solvents or abrasive sponges.
Correct chosen floor made of natural stone has a very long life, but this requires a correct placing method.