a blood-red flaw

?As far back as the sixteenth century, some societies had viewed diamonds as talismans of strength, fortitude, and courage, attributes undoubtedly derived from the stones? hardness, transparency and purity. Since diamonds were even more rare then than they are now, it?s not surprising that they quickly were ascribed magical qualities. Diamonds were said to reveal the guilt or innocence of accused criminals and adulterers by the colors they reflected. They were said to reanimate the dead and render the virtuous invisible. The stones were also believed to bring the wearer all forms of good fortune, unless it had a blood-red flaw in the middle, in which case it meant certain death.?

?Greg Campbell, from Blood Diamonds: Tracing the Deadly Path of the World?s Most Precious Stones, 2002. He cites as his source Kevin Krajick, Barren Lands: An Epic Search for Diamonds in the North American Arctic, 2001.