There are some stain in Marble or Terrazzo that we cannot remove from the stone by grinding or polishing as the colour/stain has penetrate into the stone and become part of the stone.
Why those stain appear on the floor? It is because
1. the stain come from ground to the marble, the waterproofing below the marble not done properly, many people will think marble floor on ground floor no need to do waterproofing, actually this thinking is not right, as the ground water / dirt may pass through the marble and appear on surface. Ground floor water proofing is important.
2. Mop the floor so wet, water remain with the wooden furniture , water turn yellow because of the wood, and yellow water penetrate into the floor and stain on it.
3.Terrazzo flooring is easy to keep the black color stain on the flooring. Those stain cannot be remove and will be there until the terrazzo tiles changed.
To pretend the stain, you can waterproof your floor before install marble flooring or use StainProof to apply on the marble surface to prevent the marble change colour.