In the decades after the 1966 crash of an Air India plane on Mont Blanc in Chamonix, France, the mountain’s ice and snow have been yielding bits of debris, such as photos, old newspapers, and in 1986 even a piece of a landing gear. Then in 2013, a French mountain climber in his 20s made the dazzling discovery of a metal box containing 6,000 precious gemstones—mostly emeralds and sapphires—worth a staggering 300,000 euros ($339,000). The climber turned in the gems to the Chamonix authorities, who sought out the heirs of the lost trove. According to French law, if the property is not claimed by the rightful owner within two years’ time, it is forfeited and to be divided equally between the finder and the authorities. Early in December, the municipality announced that the emeralds and sapphires have now officially been claimed by the municipality and the climber who found them. …