A Clean necklace is obtained by cleaning Uncleaned finds in the Varrock Museum which requires completion of the Digsite Quest. It is somewhat rare and may take a while to find (expect to clean between 100 and 1000 samples in order to get the necklace, although it can potentially take more. It often takes upwards of an hour cleaning finds to receive the clean necklace.)
After finding it, players must then talk to one of the archaeologists cleaning finds in the museum. They will teach the player how to enchant a ruby necklace to make a Digsite pendant, and they will then remove the clean necklace from the player's inventory. The necklace may be worn, although it has the same appearance as a ruby necklace.
It cannot be obtained again once it has been given to an archaeologist.