Need to restore stone? My Aunt J gave me a great tip - wash the stone with muric acid and then use stone gloss.

Of course, muric acid is highly corrosive (dangerous to fragile flesh), so you'll need a really good, heavy duty pair of gloves and a face shield. Try to keep the area well ventilated while you're working and use a small scrub brush. She tells me it will take a bit of time (labor intensive). Then, wash down with water.

After everything has dried, use stone gloss to seal and hi-light the stone. This is the product that she recommended: http://www.sandtextrade.co.uk/en/Products/CLASSIC+STONE+GLOSS.htm . Unfortunately, it seems to be primarily sold in the UK. Still, I'm sure one of the American super-stores will have something similar.

My stone fireplace is shown above. Once I paint and do a couple other odds and ends, I'll try her suggestion and post the results (a new pic) to this blog.

Best luck to all with their home improvement efforts.