QUARTZ var SMOKEY QUARTZ WITH WATER AND GAS INCLUSIONS, RUTILE INCLUSIONS, BRAZIL (large 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.

Rutile is a titanium dioxide (TiO2) mineral and represents the most prevalent natural form of this compound. There are less common polymorphs of TiO2, such as anatase, akaogiite, and brookite. 

This mineral is notable for having one of the highest refractive indices among known crystals at visible wavelengths, along with significant birefringence and high dispersion. These characteristics make rutile valuable in the production of specific optical components, particularly in polarization optics for longer visible and infrared wavelengths, extending to approximately 4.5 micrometers. Additionally, natural rutile can contain up to 10% iron, along with notable quantities of niobium and tantalum.