Agate is a type of microcrystalline quartz that is known for its vibrant colours and banded patterns. It is formed within volcanic rocks or as a filling in cavities within other rocks. Agate is composed of layers of chalcedony, a variety of quartz, and often exhibits different colours and shades within each layer.

The colours of agate can vary widely, ranging from transparent to translucent and including hues of white, grey, blue, green, yellow, red, and brown. These colours are often arranged in concentric bands or parallel lines, creating unique and mesmerising patterns. The banding in agate is caused by the deposition of different mineral impurities or changes in growth conditions during formation.