The website 'MovieSniped.com' posted for auction a very cool Smallville replica prop of the "Stone of knowledge."
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"This is a smallville stone of knowledge airstone prop replica. This is the pewter stone (silver). This stone is hollow on the inside. This has been on display and well taken care of...The black stone and red cloth are not included in this auction..." ~ moviesniped.com
Unfortunately, for anyone interested the eBay auction for this prop ended a while ago. It sold for 405.00 U.S. dollars. The 'stone of knowledge' played a central part throughout the show's 4th season. Most notably in the episode "Sacred" when Lana, while possessed by her ancestor Isobel, battled it out with Clark for it. Also, in the second image above, you will see "Lana's stone" containing the Kryptonian symbol connected with Lana.
Season 4 - Episode "Sacred"
To check out the eBay auction: CLICK HERE
To see another 'Smallville' Lana Lang related prop posted by moviesniped.com: CLICK HERE