Subscribe | UPI Odd Newsletter Subscribe CHICAGO, Dec. 16 (UPI) -- What had been one of the greatest treasures in the University of Chicago library, a Byzantine copy of the Gospel of St. Mark, is a fake, officials said. The authenticity of the hand-lettered Gospel has been debated for 20 years, the Chicago Sun-Times reported Wednesday. Margaret Mitchell, who teaches at the university Divinity School, said a blue pigment on one page was determined not to have been created until 1794, a suspicious circumstance given that the volume was supposed to date from the 14th century. Advertisement Since then, researchers have used carbon dating and examination of pages under an electron microscope. The university bought the Gospel from a Greek family in the 1930s. "The evidence points quite directly to it being fabricated for the antiquities market," Mitchell said. Mitchell said whoever created the forgery was skilled at the trade, using some sort of brownish-black liquid on the edges of the pages to duplicate the soot that built up on volumes read by candlelight. Mitchell said the work probably took months.