Magnethaardeid

Magnethaardeid is a rare ferromagnetic mineral with a composition dominated by iron and magnesium in a silicate framework. It is characterized by a metallic luster, steel-gray to black color, and pronounced magnetism at ordinary temperatures. The mineral crystallizes in a brittle form, commonly as small grains embedded in ultramafic rocks.

The name magnethaardeid combines the word magnet with the suffix -haardeid, used in mineral nomenclature for exotic silicate minerals. The type locality is the Schelwind ultramafic complex in the Central Alps, where magnethaardeid was first described in 1987 by researchers L. Kestrel and I. Rao.

Occurrence and geologic setting: Magnethaardeid is found in hydrothermal veins cutting serpentinite and dunite, often together with magnetite, olivine, and pyroxene. It appears as intergrowths with other ferric silicates and as crustal grains in cumulate rocks.

Properties: It exhibits a metallic luster and opaque appearance, with a Mohs hardness estimated at 5.5–6.0 and a measured density around 5.9–6.3 g/cm3. It is strongly magnetic and lacks cleavage, with a conchoidal to uneven fracture. Crystals are rare; when present, they form prismatic or tabular shapes in the orthorhombic system.

Formation and synthesis: Magnethaardeid is thought to form through high-temperature interaction of iron- and magnesium-rich rocks under reducing conditions, with silicate polymerization controlling its structure. Laboratory synthesis has shown that it can be produced by solid-state diffusion at temperatures above 800°C in controlled atmospheres.

Uses and significance: Due to its rarity, magnethaardeid has limited commercial use, but it is of interest to mineralogists and magnetism researchers for its ferrimagnetic behavior and potential insights into magneto-structural coupling in silicates. Specimens are sought by collectors and educational displays.