Definition: A gemstone that is a striped version of chalecedony quartz, agate forms in layers in many colors and textures by filling-in an indentation or cavity in another rock.
When agate is sliced, its concentric layers become obvious, sometimes appearing as bands that resemble the growth rings of a tree trunk. The bands can be different colors, widths and textures. Some even look like a bed of moss or a forest scene.
Some examples of agate have splotchy areas of color instead of round rings.
