mineralens

Mineralens is a term that appears in some mineralogical discussions to describe lens-shaped features within minerals that influence light transmission. It is not a standard term in mainstream petrography, and many researchers prefer more specific descriptors such as lens-shaped inclusions, exsolution lamellae, or optical zonation.

Definition and forms: A mineral lens refers to a discrete body of one mineral surrounded by another, with a convex or concave boundary that yields a distinct refractive contrast from the host mineral. These features may occur as isolated pockets or elongated, curved regions aligned with crystallographic directions.

Origins: Mineralens can form through several processes, including exsolution during cooling, metasomatic replacement where one mineral alters another, deformation that concentrates contrasting minerals along specific planes, or growth zoning that produces curved interfaces. Their boundaries and internal textures reflect the host rock’s pressure–temperature path and chemical history.

Optical properties and detection: In thin sections viewed under transmitted or polarized light, mineral lens features can produce notable optical contrasts, relief, or interference colors. In some cases they act as microlenses, bending or channeling light within the mineral. Identification and characterization commonly rely on petrographic microscopy complemented by microprobe analysis or imaging methods.

Occurrence and significance: Mineralens are reported in various rocks, including metamorphic belts and pegmatites, where contrasting refractive indices or compositional differences exist. They provide information about paragenesis, deformation, and chemical evolution, though their terminology remains less standardized than more widely used descriptors of inclusions and zoning.

See also: Inclusions, Exsolution lamella, Optical mineralogy.