Serpentinite Rock

Serpentinite Rock

Elin McCoy/Bloomberg

Pierre-Marie Luneau holds a chunk of serpentinite rock plucked from La Butte de la Roche vineyard, near his family's Domaine Pierre Luneau-Papin in Le Landreau, France. The hill on which the vineyard is located is a geological landmark in the Muscadet region of France's Loire Valley.