Assertion: pentelic marble | /r/HasProperty | exposed to air
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Source sentences:
text: The Pentelic marble mined from Mount Pentelicus north of Athens, from which the sculptures are made, naturally acquires a tan colour similar to honey when exposed to air; this colouring is often known as the marble's "patina" but Lord Duveen, who financed the whole undertaking, acting under the misconception that the marbles were originally white probably arranged for the team of masons working in the project to remove discolouration from some of the sculptures.