Silicone is polymers. Silicones are used in sealants.

Silicones are key to the construction and renovation of commercial and cottage – from glass-walled highrise to boost energy-efficient architecture. At home, silicone sealants and caulks are used to prevent damage from moisture and bacteria build-up.

The silicone should be high quality, ideally at least "food grade."  The higher the quality, the lower the possibility of leaching chemicals this leaching will cause stains, especially to marble.

Old Stonemasons Ramblings: Joint finishing solutions what a game changer! These are sprayed over the rough silicone bead ( NOT BEFORE ) then tooled with a silicone tool/paddle pop stick. The unwanted silicone is removed from the joint in one smooth action. Before this product stonemasons and tilers would use a diluted (Watered down) solution of dishwashing liquid and water. This enhanced the ability of mould to grow on the silicone joint in wet areas. What was happening, dishwashing liquids contain citric acid which attacks the surface of the silicone leaving minute caves in the silicone. After a few weeks/months the mould would grow in these very minute flower pots.