Agate

Chemical composition: silicon dioxide
Formula: SiO 2 (SI=silicon, O=oxygen)
Color: multi-colored
Luster: waxy
Hardness: 6.5–7
Specific gravity: 2.58–2.64
Amount of transparency: translucent

Agate is a many-colored, banded form of chalcedony (a variety of quartz) that has been deposited in cavities or in veins. Beautiful agates that were transported by glaciers during the Ice Age are found in the Glaciated Region in Kansas.