I'm passing this along because these solutions for etching problems helped us. Credits and website are given at the end . I have no financial interest in this and I am just a home owner with no commercial interests. I helped my mother with her counter top etch and grease marks. Enjoy reading !
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Removing Stains from Marble and other Natural Stones

Some of the more common poulticing materials and powders are:
cotton balls
paper towels
gauze pads

Stain Removal Guide
All solutions are given starting with the gentlest method first.

1. Iron Stains (rust)
Poultice with on the the following:
a. Sodium citrate and glycerin or
b. Ammononium Oxalate or
c. Oxalic Acid or
d. Orthophosphoric Acid and Sodium Salt of EDTA in water or
e. Dilute Hydrofluoric Acid or
f. cannot be removed, is part of the stone

2. Ink
Poultice with one of the following:
a. Light colored marbles only use Bleach or Hydrogen Peroxide;
b. Dark marbles use Lacquer Thinner or Acetone;
c. Methyl Chloride

3. Oil Based Stains (grease, cooking oil, tar, food stains, etc.)
Clean with:
a. Scouring Power with Bleach or
b. Household Detergent or
c. Ammonia or
d. Mineral spirits or
poultice with:
e. Baking Soda or
f. Mineral Spirits or
g. Methyl chloride

4. Organic Stains (paper, tea, coffee, cosmetics, fruit, tobacco, etc.)
a. Pour Hydrogen Peroxide 35% directly on stain and add a few drops of ammonia, leave until bubbling stop ors
b. Repeat above but add poultice or
c. Acetone or Toluene or Xylene

5. Efflorescence
Poultice with:
a. Distilled Water

6. Copper Stains
Poultice with:
a. Ammonium Chloride or
b. Ammonium Hydroxide

7. Biological Stains (Lichens, algae, moss, fungi, mildew, etc.)
Clean with:
a. Dilute Ammonia or
b. Bleach or
c. Hydrogen Peroxide or
d. Sodium Hypochiorite

8. Wax (Acrylic yellowing coatings)
Strip with:
Alkaline Stripper

9. Urethane Coatings
a. Methyl Chloride or
b. Grinding

10. Crystallization coatings
a. Strip with Oxalic Acid based Stripper or
b. Methyl Chloride

11. Paint
a. Alkaline Paint Remover
b. Methyl Chloride

12. Grout and Thin Set Residue
a. Scrub with neutral cleaner and red pad or
b. Re-polish

13. Scratches
a. Re-polish or
b. Re-hone

14. Streaking
a. Buff with felt pad-dry or
b. 0000 Steel wool-dry or
c. Re-polish

15. Acid/Alkaline Etching
a. Re-polish or
b. Re-hone

16. Stuns/Crystal Fractures
Re-hone

17.Water Spots and Rings
a. Buff with a dry 0000 Steel wool or
b. Re-polish or
c. Re-hone

18. Discoloration
Clean with:
a. Alkaline Stripper or
Poultice with:
b. Bleach or
c. Hydrogen Peroxide or
d. Re-hone and polish

19. Swirl Marks from steel wool
a. Re-polish or
b. Re-hone

20. Random Dull Spots
a. Check for etching or
b. Re-polish

21.Excess Lippage
Grind/re-hone/polish

22. Warped Tiles
Remove and Replace

23. Loose Tiles
Remove and Reset

If the problem is serious in nature or too large in size. consider using the services
of a qualified stone restoration expert in your area.

Frediric M. Hueston has a degree in Chemistry and is also an experienced and accomplished marble and stone craftsman, Founder and president of Cambridge Floor Care Systems, based in Winter Park, Florida. Hueston is a recognized leader in the marble and stone care and restoration field.

Hueston is a member of Building Stone Institute's Marble (and stone) Care and Maintenance Committee.
http://eurotechmarble.com/removingstains.htm