fenkelite

Fenkelite is a rare silicate mineral characterized by layered sheets of silicate tetrahedra linked to octahedral layers of metals. It was first described from Fenkel Ridge and is named after the locality. The mineral typically forms slender prismatic crystals and is of interest to mineralogists and materials scientists for its distinctive layered structure.

Chemical composition and structure: The general formula is (Fe2+,Mg)2Si4O10(OH)2, with iron-rich varieties exhibiting a darker color. The structure consists of silicate sheets bonded to metal-oxide layers, producing a flexible framework that influences its physical properties. Substitution by Mn and Ti can occur, providing minor chemical variation between samples.

Physical properties: Fenkelite has a Mohs hardness of about 5.5 to 6 and a specific gravity near 3.2 to 3.4. It ranges in color from pale brown to olive-green and shows a vitreous to pearly luster on cleavage surfaces. The mineral crystallizes in the monoclinic system and commonly displays a prismatic habit with good basal cleavage.

Occurrence and associations: Fenkelite is found in hydrothermal veins and contact metamorphic zones within mafic to ultramafic rock sequences, with Fenkel Ridge as a principal locality. It is typically associated with magnetite, calcite, and diopside, among other silicate and oxide minerals.

Uses and significance: Due to its layered structure, fenkelite has been investigated as a potential ceramic additive and catalyst support. Its ion-exchange potential and thermal stability also attract interest for niche applications in materials science and environmental remediation.

Etymology: The name fenkelite honors Fenkel Ridge, the locality where the mineral was first identified.