ilite

Ilite is a mineral belonging to the mica group, characterized by its silicate composition and layered structure. Chemically, it is composed primarily of aluminum silicate hydroxide, with the formula Al₂Si₄O₁₀(OH)₂. This mineral is closely related to muscovite and is often found in metamorphic rocks, particularly those formed under low-grade conditions. Ilite typically forms during the diagenesis of shales and clays, where it replaces unstable minerals like kaolinite.

The name "ilite" originates from the Greek word *ilex*, meaning "oak," though its exact etymology is debated. It was first described in the early 20th century as a distinct mineral, though it was later recognized as a transitional phase between kaolinite and muscovite. Ilite is often identified through its physical properties, including a pearly to silky luster, perfect basal cleavage, and a hardness of approximately 2–2.5 on the Mohs scale. Its color ranges from white to gray, brown, or greenish hues, depending on impurities.

Ilite is commonly found in sedimentary rocks such as shales, mudstones, and some sandstones, where it serves as an indicator of burial depth and diagenetic conditions. It is also present in some igneous and metamorphic rocks, though less frequently. Due to its fine-grained nature, ilite is often studied using X-ray diffraction (XRD) and other analytical techniques to distinguish it from similar minerals.

In industrial applications, ilite is sometimes used as a filler in ceramics and paints, though its use is less common compared to other micas. Its occurrence in clay deposits also makes it relevant in the production of bricks and other construction materials. Geologically, ilite plays a role in understanding the transformation of clay minerals during sedimentary rock formation and metamorphism.