Terebrantian

Terebrantian is a proposed mineral concept described to represent an iron- and magnesium-rich silicate characterized by elongated, prismatic crystals that resemble drill-bit shapes in hand samples and thin sections. It is not yet recognized as a formal mineral species by the International Mineralogical Association (IMA), and its status remains provisional in the field of mineralogy.

The name derives from the Latin terebra, meaning “drill” or “auger,” reflecting the apparent tapering, needle-like habit observed in some specimens, with the suffix -antian forming the standard geological descriptor. The term has appeared in several field reports and petrographic studies citing distinctive crystal habit and associated mineral assemblages.

Physical properties of terebrantian are described as dark gray to olive-green in color, with slender prisms that may extend to several centimeters. The crystal system is reported as monoclinic in some descriptions and orthorhombic in others, with a hardness near 6 on the Mohs scale. Luster is vitreous, and cleavage is generally good on one plane ({010}) with a conchoidal to uneven fracture. The mineral is chemically dominated by iron- and magnesium-rich silicate phases, with trace aluminum and titanium; compositions are described as variable within a narrow iron-magnesium range, reflecting solid-solution among related silicates.

Occurrence is reported in hydrothermally altered ultramafic rocks within ophiolite complexes, often in association with olivine, pyroxene, magnetite, and chlorite. Formation is linked to high-temperature fluid activity during serpentinization and related metasomatic processes.

Taxonomic status remains unsettled, with researchers calling for additional petrographic, crystallographic, and geochemical analyses to establish a formal chemical formula, definitive crystal structure, and whether terebrantian should be accepted as a distinct mineral species or as a varietal member of a broader silicate group.