Which mineral is commonly used in the phyllosilicate group?

The mineral commonly associated with the phyllosilicate group is biotite. Phyllosilicates, also known as sheet silicates, are characterized by their layered structure. This group includes minerals that have a two-dimensional sheet-like arrangement of silicate tetrahedra, which allows them to cleave easily along these planes. Biotite is a mica mineral that exemplifies this structure, consisting of sheets of silicate tetrahedra bonded to octahedral sheets of cations.

Biotite's distinctive characteristics include its dark color, perfect cleavage in one direction, and its ability to form in thin, flexible sheets. This property is a direct result of its phyllosilicate structure, which enables it to be easily separated along the layers. The presence of iron and magnesium gives biotite its typical coloration and makes it a common component in igneous and metamorphic rocks.

In contrast, quartz and feldspar are part of different silicate groups: quartz belongs to the framework silicates, which have a three-dimensional interconnected structure, while feldspar is part of the tectosilicates. Fluorite, on the other hand, is a halide mineral and does not belong to the silicate group at all.