Diamond Head is a volcanic tuff cone on the Hawaiian island of Oʻahu and known to Hawaiians as Lēʻahi (pronounced [leːˈʔɐhi]). The Hawaiian name is most likely derived from lae (browridge, promontory) plus ʻahi (tuna) because the shape of the ridgeline resembles the shape of a tuna's dorsal fin. Its English name was given by British sailors in the 19th century, who named it for the calcite crystals on the adjacent beach.