Ko'i
Basalt stone adze
Found on Napuka Atoll in the Tuamoto Archipelago
Between 1929 and 1934 Bishop Museum anthropologist Dr. Kenneth Emory collected 19 basalt koʻi, or adzes, in excavations on the low coral islands of the Tuamotu Archipelago. Koʻi were one of the basic implements of the Polynesian toolkit, and were used for felling trees and carving wood.
Most koʻi throughout the Polynesian Triangle are made of stone, typically basalt which is a fine grained volcanic rock (essentially cooled lava) that can be shaped into a number of stone tools for pounding, chopping, and cutting. Low coral islands like the Tuamotus do not have basalt—the volcanoes that built the islands had slowly subsided and coral reefs grew atop their submerged peaks. Toolmakers on low coral atolls sometimes turned to shell or other materials for their adzes, but heavy fine grained stone was superior.
Compared to adzes from the large volcanic islands of Polynesia like Hawaiʻi, Tahiti. or Aotearoa (or New Zealand), the Tuamotu koʻi is small. Some Hawaiian koʻi are more than 60cm (or two feet) long. Stylistically, the Tuamotu ko'i is distinct from the tools made in other Polynesian Islands, so it was probably made locally.
The koʻi that Emory uncovered were made of material from a high volcanic island, far from the small atolls of the Tuamotus, but where? Until modern geochemical analysis techniques were developed, there was no way to answer this question.
In 2007, researchers took small samples from the 19 koʻi found by Dr. Emory and compared the trace element and radioactive isotope signatures of each to sources of basalt from around the central Pacific.
Not unexpectedly, most of the basalt came from nearby volcanic islands in the Marquesas, Pitcairn, and Austral Islands. But the fingerprint returned by adze c.7727 matched that of a basalt quarry on the Hawaiian island of Kahoʻolawe, 4,000 km to the north.