My 1600’s Cornish cottage has very old, large Delabole slate tiles on the floor of the lounge and hall. They are uneven and cracked where they’ve lifted over time and make a great feature as to the originality of the property. However, the slate has been badly marked by previous owners when moving furniture around. Picture show this. How can I best restore the surface and remove the scratches, and how to renovate the grout which has effervescence coming from it 
