Which mineral is commonly used in the phyllosilicate group?

The mineral commonly associated with the phyllosilicate group is biotite. Phyllosilicates are characterized by their layered structure, which allows them to form sheets. Biotite is a mica group mineral that exhibits this distinctive layering, making it a classic representative of phyllosilicates.

Micas, including biotite, have a perfect cleavage in one direction, which aligns with their layered structure, allowing for easy separation into thin sheets. This property is not just a hallmark of their physical structure but also affects their properties and uses in various applications.

Other minerals listed do not belong to the phyllosilicate group. Quartz is a framework silicate, feldspar is a tectosilicate, and fluorite falls into the category of halides, which is distinctly different from the silicate group. Hence, biotite stands out as the correct choice when identifying a mineral from the phyllosilicate group.