Keelingin

Keelingin is a rare green silicate mineral named after the Keeling Islands in the Indian Ocean. It was described from hydrothermally altered basaltic rocks on a small islet and is characterized by olive-green to emerald-green prismatic crystals with a vitreous luster. Crystals are typically tiny, seldom exceeding a few millimeters in length, and crystallize in the monoclinic system.

Chemically, Keelingin is a potassium–iron silicate. Its structure consists of silicate tetrahedra linked into chains, with interstitial potassium and iron occupying sites between the chains. Minor aluminum and sodium are present, and trace amounts of magnesium have been reported. The mineral’s calculated density is about 3.2 g/cm³, and its hardness is around 6.5 on the Mohs scale.

Occurrence and formation: Keelingin forms during hydrothermal alteration of coastal basalt in tropical island environments, where hot fluids interact with evaporitic or seawater-influenced sediments. The type locality is on a single islet in the Keeling archipelago; additional specimens are reported from a second nearby site, but the overall distribution remains extremely restricted.

Name and classification: Keelingin is placed in the silicate mineral group, with the name reflecting the geographic origin and following standard mineral-naming conventions by appending the suffix -in. The mineral is of interest mainly to researchers studying coastal hydrothermal systems and silicate crystallography.

Uses and research: Due to its scarcity, Keelingin has no practical industrial applications. It is studied for crystal chemistry, isotopic composition, and potential as a tracer in paleoenvironmental reconstructions, using X-ray diffraction, electron microprobe analysis, and Raman spectroscopy.