Eduard Guebelin, 91, who demonstrated that "inclusions" that were once considered undesirable flaws can indicate the origins of diamonds and other precious stones, died March 15 in Lucerne, Switzerland, of natural causes.
Born to a Swiss watch-making family in Lucerne, Guebelin studied at the University of Zurich and earned a doctorate in mineralogy from the University of Vienna. In 1939, he also received a diploma from the Gemological Institute of America in Los Angeles, which publishes the quarterly journal Gems & Gemology.
