Alan Greenspan seemed to say that they are.
"Greenspan waved off the necessity for the CFTC to regulate gold derivatives, telling Congress to fear not, that the central banks stand ready to lease gold in increasing quantities should the price rise.
http://www.financialsense.com/editorials/casey/2007/0125.html "
It catches my attention that the quote is selectively presented. What came before the quotation marks? Probably not the words "fear not". I would have to see the whole testimony in its proper context to give it any validation.
Your source, Doug Casey, is a stock tout who makes money selling hot stocks, or stock tips, to suckers. Why should I believe anything he says?