spinalt

Spinalt is a mineral species characterized by an elongated, spine-like crystal habit observed in hydrothermal vein assemblages. The name derives from the Latin spina, meaning spine, reflected in its distinctive prisms and needle-like projections.

Occurrence and discovery: first described in 2021 by researchers from the Oceanic Mineral Research Institute after specimens were recovered from serpentinized ultramafic rocks at a mid-ocean ridge setting. It has since been identified at comparable vent-field localities, suggesting a preference for high-temperature, silica-rich hydrothermal systems.

Crystal structure and properties: Spinalt crystals are typically elongated prisms with flattened faces that converge to spine-like tips. Color ranges from pale gray to blue-gray; translucent to opaque. It crystallizes in the monoclinic system and forms thin, acicular crystals that may aggregate into radiating clusters. The mineral consists mainly of silicate frameworks with dopant cations such as magnesium and iron occupying octahedral sites. It has a Mohs hardness of about 6 and a relatively low to moderate specific gravity around 3.2–3.4. Under ultraviolet light, Spinalt may show weak luminescence; it exhibits a modest pyroelectric response.

Formation: Spinalt is believed to form through high-temperature alteration of ultramafic rocks in silica-enriched hydrothermal fluids, where directional growth promotes the spine-like habit. Geochemical conditions, including the availability of magnesium and iron dopants, influence its crystallography.

Uses and research: In research contexts, Spinalt is studied as a model for anisotropic crystal growth and for potential ceramic applications demanding thermal stability and low fracture propagation. Synthesis attempts and stability testing under varying pressure and temperature are ongoing.

See also: list of minerals, crystal habit, monoclinic crystals.