Kumerus

Kumerus is a mineral species described in mineralogical literature as a hydrated aluminosilicate. The name is derived from Kumera, the island group where the type material was collected, combined with the Latin suffix -us.

Discovery and naming: It was first reported in 2019 by researchers from the Institute of Geosciences. The type locality is a hydrothermally altered basalt on Kumera Island, and the identification of Kumerus relied on integrated mineralogical techniques, including X-ray diffraction and electron microscopy. The designation Kumerus was proposed to distinguish the mineral within a complex assemblage of hydrous silicates found in the area.

Description: Kumerus crystals are typically prismatic to tabular, colorless to pale blue when hydrated. It has a vitreous luster and a Mohs hardness around 5. Optical properties include distinctive refractive indices that aid in its identification in hand specimen and thin section.

Composition and structure: The proposed formula for Kumerus is (Mg,Fe)2Al4Si6O20(OH)4·nH2O, reflecting a layered silicate framework with octahedrally coordinated aluminum and magnesium and interlayer water. The structure accommodates water molecules between layers, contributing to its hydrous character and diagnostic infrared absorption features.

Occurrence and paragenesis: Kumerus forms in low-grade metamorphic or hydrothermal environments within volcanic arcs. It is commonly found in association with montmorillonite, chlorite, and quartz, suggesting formation during fluid-rock interaction at relatively modest temperatures.

Distribution: To date, documented samples originate from Kumera Island and one nearby outcrop. Material remains limited, and further mining and analysis are needed to better define its geographic range and variability.

Significance: The mineral is studied for its potential to record fluid histories and water content in metamorphic systems. Isotope analyses of its hydrous content may provide insights into paleo-temperature conditions.

See also: list of minerals, hydrous silicates, metamorphic minerals.