Marble and granite tables, furniture pieces or countertops that are very old or have been outside for many years typically have several cleaning issues to address in order to restore the shine, color, and beauty.
Often the stone has stains, etch marks, embedded dirt and is just overall heavily-worn and weathered. Professional restoration is usually the best option.
However, if you really want to try and tackle such a complex and multi-step restoration project yourself, then try the following:
1. Thoroughly scrub the surface several times using the Heavy Duty Tile & Grout Cleaner (1 QT). This will clean all grime and soiling that is right at the surface.
2. If dark spots (stains) remain, then try to remove them using the Marble & Granite Stain Removal Poultice Powder. Regular cleaning methods will not remove stains (which occur from a liquid substance absorbing into the surface). This will not remove dirt and dust that has been physically embedded in the stone over time or stains that are now very deep into the stone.
If steps #1 and #2 are successful, then you can leave the table as is. It should be relatively clean, but may have a matte or honed type finish.
If you desire a shiny polished finish, then the next step depends on the type of stone.
To polish granite you'll need to hire a stone restoration professional. Repolishing granite requires significant knowledge, skill and experience and use of special tools and abrasives.
To polish marble, travertine or limestone you can use the ETCH REMOVER / Marble Polishing Powder. Marble is much softer and repolishing can be done by hand with this DIY product. However, when polishing a large area it can be difficult to achieve an even shine. This product is really designed for restoring small spots and glass-rings that result from acid etching.
Also, if the marble is too raw and rough from wear and weathering, then this product may not bring it to a high shine. Polishing marble is done in steps depending on the condition of the stone surface. Different products and methods are needed at each step. This product is meant for use as the final step to polishing on a stone surface that is already nice and smooth.
However, if the table still looks dirty and mottled after steps #1 and #2, then the stone likely needs to be ground down (removing the stained, damaged surface and embedded dirt) to reveal fresh marble and then refinished to a polish. This is a process for a stone restoration professional.
My recommendation is that you have it professionally restored. Again, you can try the DIY procedure outlined above, but since old stone or marble and granite with many years outside are usually heavily-weathered there is no guarantee that it will be successful. Of course, you could still have it professionally restored after trying it yourself if you so choose.
Once restored it would be a good idea to apply a quality sealer like the SenGuard Permanent Sealer to prevent future staining. Although, note that marble, travertine, and limestone left uncovered outside will become weathered again in a relatively short period. These stones are soft and the continuous cycles of sun, wind, rain, acid rain, ice, and snow, etc. will wear away the surface finish and potentially cause soiling. It is best to cover marble tables, etc., or simply allow them to weather naturally. Granite is much harder and will not wear from weather as quickly.