Gypsum

specimen number:
2292303

location:
Makapuu, Oahu Island, Honolulu Co., Hawaii, USA

description:
A floater cluster of bladed gypsum crystals. Complete all around. Interesting locality example for the species.

The gypsum specimens found near Makapuu Point on the eastern coast of Oahu, Hawaii, occur primarily as the colorless-to-tan crystalline variety known as selenite. Geologically, these crystals are non-magmatic evaporite minerals that did not form directly from volcanic eruptions; instead, they precipitated within coastal sediment pockets, soil banks, or weathered volcanic ash layers where calcium-rich groundwater or trapped seawater underwent intense evaporation under arid conditions. This localized environment allowed sulfate and calcium ions to concentrate and crystallize into small, tabular prisms and occasional intergrown clusters. There has never been an organized commercial mining or quarrying operation for gypsum at Makapuu, as the deposit completely lacks industrial scale or economic viability. Instead, the history of the locality is defined entirely by low-impact, casual surface collecting by local rockhounds, students, and mineral hobbyists who surface-collected the loose crystals out of exposed dirt banks and coastal paths during the mid-to-late twentieth century, leaving the site strictly an occasional field-trip locality rather than an active mineral production zone.

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