Region 7: Hawai'i

The uniform geology of the Hawaiian Islands does not produce the variety of mineral resources seen in many other parts of the world (Figure 5.20). However, human development has spurred demand for building materials, which, in turn, has driven the development of basalt and limestone resources. In ancient times, Hawaiians used dense basalt for tools and implements. Evidence of quarry sites once used for these purposes can be found throughout the islands. The Hawaiians also used basalt rocks for building hut bases and ceremonial walls (Figure 5.21).

Figure 5.20: Mineral resources of Hawai’i.

Figure 5.21: Impressive ancient dry stone construction at Pu’uhonua O Hōnaunau National Historical Park, Hawai’i Island.

The arrival of Europeans and the subsequent development of the Hawaiian Islands led to an expansion of the construction industry, ultimately requiring more materials. More recently, some companies have been working to develop deposits of extremely weathered soils for their aluminum potential.

The US Geological Survey divides the current utilized mineral resources of Hawai’i into three categories: crushed stone, construction sand/gravel, and gems.

Crushed stone is Hawai’i’s largest mineral resource, making up over 85% of the state’s mineral production resources (Figure 5.22). Crushed basalt is used for a variety of purposes in the construction industry, such as in road bases and as an aggregate in concrete, drainage, and stone retaining walls. Sand made of cinder from cinder cones is also sought after as a landscaping material. Limestone from emerged Pleistocene-age reefs, and the coastal carbonate sand dunes that fringe O’ahu and older Hawaiian islands, has been used to make cement products.

The “gems” mined in Hawai’i are limited to black and precious corals. Approximately $150,000 a year of this material is taken from the waters off the coasts of O’ahu and Maui to be used for jewelry production (Figure 5.23). It is often thought that the olivine (peridot) sold in stores around the islands is sourced from the local rocks, but collecting and selling olivine is considered disrespectful in traditional Hawaiian custom. It is therefore illegal to extract it from most sites, and the olivine sold in Hawai’i is actually sourced from locations outside the islands.

Figure 5.22: Crushed stone quarry nestled in the hills of O’ahu.

Figure 5.23: Coral bracelet.