Diamond Head, Hawaii

Diamond Head is a volcanic tuff cone on the Hawaiian island of Oahu and known to Hawaiians as Lēahi, most likely from lae 'browridge, promontory' plus ahi '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 mistook calcite crystals on the adjacent beach for diamonds.GeologyDiamond Head is part of the system of cones, vents, and their associated eruption flows that are collectively known to geologists as the Honolulu Volcanic Series, eruptions from the Koolau Volcano that took place long after the volcano formed and had gone dormant. The Honolulu Volcanic Series is a series of volcanic eruption events that created many of Oahu's well-known landmarks, including Punchbowl Crater, Hanauma Bay, Koko Head, and Mānana Island in addition to Diamond Head.Diamond Head, like the rest of the Honolulu Volcanic Series, is much younger than the main mass of the Koolau Mountain Range. While the Koolau Range is about 2.6 million years old, Diamond Head is estimated to be about 500,000 to 400,000 years old.