Granite typically does not etch from acidic foods, drinks or other corrosive chemicals. However, there can be other variables involved when seeing dull and light spots on granite. Nearly all suspected etching on granite involves polished black granite.
Here are the likely reasons:
1. Your granite has been etched. Granite will not etch easily and this is usually not a problem with common foods, drinks, and products. However, granite can and does etch upon contact with very strong acids and/or from repeated exposure to acidic foods or cleaning products.
For this reason, you should only use products made specifically for cleaning stone. Also, some rare varieties of granite (or stones sold as "granite) do exist typically referred to as "mutt" stones since they are of a mixed mineral composition that in some cases does etch.
Again, this is a rare occurrence, however, if #2 or #3 do not apply, then there is no other explanation. This applies to either polished or honed granite.
If either of the above is the case, then your only option is to hire a stone restoration professional to refinish your stone.
2. A resin was applied. Resins are applied to some granite slabs to fill voids and pits. This is common and acceptable, yielding a better granite slab. However, some resins can etch. If so, then you'll need to strip the resin, or possibly it can be re-finished by a stone restoration professional.
This is an issue with polished granite. It could potentially occur on a granite slab that was resined and then honed or leathered, but uncommon.
3. Your granite has been "doctored". This is a problem particularly with so-called "black" granite and on polished stones only. Although, it could still potentially cause a problem if the granite was originally polished and then the slab was honed or leathered.
There is more demand for black granite, therefore it is more expensive. But some granite is gray, so factories (mainly in India and China) apply a black coloring to the stone.
This is not an acceptable practice because, unlike a resin, this process falsely changes the appearance of the stone. Well, this dye coating is sensitive to acids and will etch upon contact with many/most cleaning products, many foods, drinks, and personal products creating dull and light-colored spots.
If your stone has been doctored, you'll need to remove the black coating on the entire surface. This can be difficult and usually requires stripping the surface with potent solvents.
To learn more about this issue please go to our Questions page and type "doctored granite" into the search box. You'll be presented with several pages of detailed information regarding this issue and what to do about it.