What are the names of the granite and marble you have chosen? It's not the color that determines whether it needs to be sealed.

Hmm, I don't know the names. They were already installed in the house when we purchased it. The builder, annoyingly, does not like to give me "unnecessary" information; it's like pulling teeth to ask him for anything!

Is there a way to figure out what kind of granite and marble they are without knowing the names?

Do you have samples of your granite? You could try testing a sample with various substances such as lemon juice, oil, red wine, etc. to see if it absorbs any. Alternatively, you could sprinkle a little water on the counter and see if it beads up. Can you contact the fabricator who installed the counter for the builder?

As far as marble goes, I think all marble will benefit from sealing to prevent staining BUT sealing will not prevent marble from etching.

All marble should be sealed. AS for the granite, you don't really need to find out the name of it. Just take a sopping wet sponge or rag and lay it on the granite for a few minutes. Then take it off, and wipe up any water that might still be on it. If there's a dark area where the stone was wet, you need to seal it.

What sealer? I was wondering too. I have a granite which nothing bothers and a vanity top which leaves dark stains when water sits on it. It disappears when it dries.

Please tell me what brand sealer - and can I will do this myself?

Thanks,
Jane

You need to try Bill's suggestion and determine whether or not the granite needs sealed. If you try to seal granite that is not porous (doesn't need sealed), the sealer will "sit" on top, forming a cloudy, dull film on the granite's surface. It will then need to be removed with a sealant remover product. I know this because our granite installer attempted to seal our non-porous Fashion Green granite and we had to remove the sealant to restore our tops to a shine.

Great, thanks for all your input! This is exactly the info I needed. I will "test" the granite and marble as suggested to find out if they've already been sealed or if they need it.

No need to test the marble. I'll tell you right now-- unless it's a serpentine marble (usually dark green with lightning bolt type veining to it), it needs a sealer.

As for recommendations, one of two-- Miracle's 511 Impregnator, or Stone Tech Impregnator Pro, and yes, it's very easy to seal. Take an old towel or cotton t-shirt and cut it in half. Use one side to wipe the sealer on. Let it set for about 5 minutes or so, and then take the other half and buff off the excess. Easy as pie, but time consuming, so you could really save yourself some money doing it yourself.