Today, to my surprise, I discovered that marble is not a durable material. After 150 years, signs of decay appear, and after 300-400 years, it completely deteriorates. Under the open sky, especially in places with variable humidity, it quickly gets covered with stains and crumbles. Granite and basalt, on the other hand, are a completely different matter.
Old marble statues that you see in museums are often heavily “patched” by restorers, both modern and from past centuries, plus they spent most of their history in a dry and stable climate (often artificially created, in those same museums).
I’ll also throw in another fact—apparently well-known, but relevant to the discussion. It seems that many Greek statues, probably even all of them, were painted, and what we now see is not what their contemporaries saw or how they were intended by the sculptor. I assume that we wouldn’t like the painted version now; they seem too gaudy for us. There are convincing evidences that many were painted, and it can be confidently assumed that painting was a common practice at the time, but it seems unclear whether there was a context in which the sculptures remained unpainted from the beginning, and why.
Illustration: “Ugolino and His Sons” by Jean-Baptiste Carpeaux
Hi, I'm Rauf Aliev. 