I have been researching Zeus' throne, and have found several sources that say the throne was made of black marble. One source, Robert Graves, was even more specific, saying it was Egyptian black marble. I am now trying to find out how that would have been written out. The nearest I have been able to decipher was the individual corresponding words: Aigýptios mélās mármaros (Αἰγύπτιος μέλας μάρμαρος) I am not fluent in ancient greek, Hellēnikḗ (Ἑλληνική), so I don't know if this is correct, grammatically, or if there is a more nuanced way to say it. I've also found the term mávro marmárino (μαύρο μαρμάρινο), but I think that is modern Greek. Any help would be greatly appreciated.
Αἰγύπτιος μέλας μάρμαρος sounds good to me. 'Egyptian marble that is black'. I could not find any ancient use of this term.
Edit: Initially I offered definitive forms here but I cannot find such examples, and none of my grammars have examples of definitive nouns with multiple adjectives. (Forms like ὁ μάρμαρος ὁ Αἰγύπτιος ὁ μέλας would indeed sound clumsy.)