Siliconilles

Siliconilles are a hypothetical class of silicon-rich silicate minerals characterized by layered silicate sheets built from silicon-oxygen tetrahedra with interlayer cations such as aluminum, iron, or calcium. The name is derived from silicon and the common mineral-group suffix -illes, reflecting its proposed family status within silicate minerals.

Discovery and occurrence: siliconilles were proposed in the mineralogical literature as a conceptual category for minerals that form under high-temperature, high-pressure metamorphic or hydrothermal conditions. They are considered rare and typically occur as accessory phases in subduction-zone rocks and other extremal metamorphic environments, rather than as major ore minerals.

Structure and properties: The structure consists of two-dimensional silicate sheets of corner-sharing SiO4 units, with interlayer cations occupying octahedral or distorted sites between sheets. Polymorphs of siliconilles may be monoclinic or orthorhombic. In general they have Mohs hardness around 5.5–6.5 and refractive indices near 1.65–1.75, with colors ranging from colorless to pale hues depending on interlayer composition.

Synthesis and potential applications: In experimental settings, siliconilles can be prepared by hydrothermal synthesis or high-temperature solid-state routes. Their tunable interlayer chemistry makes them candidates for ion-exchange materials, catalysis, and incorporation into ceramic matrices, although no commercial mineral specimen is widely exploited.

Taxonomy and naming: Several provisional species have been proposed based on variations in interlayer cation content, such as siliconille-ite and siliconillite, though the classification remains unsettled pending standardized crystallographic data.

See also: Silicate minerals, Layered silicates, Phyllosilicates.