They're carved or engraved in small parts (6)
I believe the answer is:
cameos
'small parts' is the definition.
(I've seen this in another clue)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for cameos that I've seen before include "Small stones carved with raised designs" , "Portraits in profile carved in relief" , "Small pieces of stone carved with raised designs" , "pieces of jewelry" , "Came so close to small carvings" .)