I think I can answer this from a different perspective.

It is true that ancient Greek and Roman statues were partly or completely painted and gilded, and that this fact was lost on Renaissance era antiquity revivalists. But the cultural concept of glowing white marble as beautiful does not exclusively date back to the Renaissance; the Greek word for marble directly translates to “shining stone,” and it was used unpainted in plenty of buildings and monuments — wealthy Greeks even preferred to have their homes built out of it rather than more ordinary rock.

But as to why marble would be used for sculpting if it was going to be covered up anyway, that mainly has to do with its geochemical composition, and what exactly you want in a sculpt-able rock. Rocks come in 3 classes: sedimentary, igneous, and metamorphic.

Sedimentary rocks are created when free-floating sediment and detritus is compacted and lithified into stone. It can be sculpted, but since it’s made up of pre-existing particles that have been cemented together, it has a built in “resolution;” you can’t get details more fine that the grain size of the particles that make up the rock you are working with. Sedimentary rocks usually contain silica, which is damaging to lung health and makes them unsafe to work with over time.

Igneous rocks are created when lava or magma cool. Igneous rocks are crystalline, and have different properties based on how quickly they cooled, and how much pressure they were under. Igneous rocks can range from very hard to very soft, and the individual crystals can be large to microscopic. Igneous rocks are inconsistent, less common than other types of rock, and overall difficult to work with. Plus, they usually contain silica too.

That leaves us with metamorphic rocks. These form when another type of rock (sedimentary or igneous) is subjected to massive amounts of heat and pressure, as the Earth’s natural cycles rebury and re-expose it. This process generally makes the texture of the rock more dense and more consistent, and in the case of marble, a metamorphic rock, it ends up just about in the sweet spot for sculpting.

Marble is made when limestone undergoes metamorphosis. Limestone itself is a unique type of sedimentary rock; it is made from the calcium carbonate shells of microscopic organisms, and other calcium-rich creatures like clams or coral. Since the individual grain size of limestone is plankton-sized (microscopic), and limestone doesn’t contain much silica, it’s already a good candidate for sculpting.

But once the metamorphosis process makes it more consistent, and as a bonus a beautiful white color, marble is essentially perfect for sculpting. It’s smooth which means it doesn’t wear down tools, its just hard enough to hold great detail but not so hard that it is impossible to use, and as a bonus, it’s abundant in the Mediterranean.