Scientific Name: Microcrystalline variety of quartz
Group: Silicates – tectosilicates
Chemical composition: SiO2
Colors: White, greyish-blue, brown, banded.
Formation: Hexagonal – trigonal crystal,Microcrystalline form; Uneven fracture; Waxy to dull luster; transparent to translucent.
Principal Sources: Turkey, Quartzsite, Arizona
Special Notes: Chalcedony forms in cavities, cracks, and by replacement when low-temperature, silica-rich waters percolate through pre-existing rocks, in particular volcanic rocks.