Scientific Name: Microcrystalline variety of quartz

Group: Silicates – tectosilicates

Chemical composition: SiO2

Colors: White, greyish-blue, brown, banded.

Hardness: 7

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.