QUARTZ covered with CHLORITE (cabinet)

Quartz is a robust crystalline mineral made up of silica, or silicon dioxide. Its structure consists of a continuous arrangement of SiO4 silicon-oxygen tetrahedra, where each oxygen atom is shared between two tetrahedra, resulting in the chemical formula SiO2. This classification places quartz as a framework silicate mineral in terms of structure and as an oxide mineral in terms of composition. It ranks as the second most prevalent mineral in the continental crust of Earth, following feldspar.

Chlorite minerals exhibit a diverse range of compositions, wherein magnesium, iron, aluminum, and silicon can substitute for one another within the crystal structure. A complete solid solution series exists between the two most prevalent end members, magnesium-rich clinochlore and iron-rich chamosite. Additionally, species containing manganese, zinc, lithium, and calcium are recognized. Extensive variation in composition leads to significant differences in physical, optical, and X-ray properties. Likewise, the diversity of chemical composition permits chlorite group minerals to occur across a broad spectrum of temperature and pressure conditions. Consequently, chlorite minerals are prevalent within low and medium temperature metamorphic rocks certain igneous rocks, hydrothermal rocks, and deeply buried sediments.