Quartz (variety: Agate)

Agate is the concentrically banded variety of chalcedony, which is, in turn, actually tiny fibrous crystals of quartz. The quartz crystals in agate is said to be cryptocrystalline - which means that it has a crystalline structure so fine that no distinct particles are recognizable by the naked eye, nor under the microscope, with regular magnification. The quartz fibers form vertical to the surface of other layers, forming the banded structure. Bands can be of the same color, or of a variety of colors, as shown in this specimen. Agate forms in cavities left by gas bubbles in cooling lava. Silica-rich groundwater builds layers of crystals on the cavity walls.

Group: Oxides
Catalog Number: image C09-36