Essentially deemed a quartz, its physical properties are that of a mineral. Agate is found all throughout the world, including the United States, such as Washington and Montana, to name a few. All agates are formed in the cavity of volcanic rocks or eruptive lava. As the lava cools, gases form bubbles, which are eventually solidified, forming a cavity. As time goes on, long after the rock has solidified, water, which is carrying the silica solution, will penetrate into the leftover bubbles, forming a silica-like gel. Eventually, the cavity hardens, all while the water is lost. During this crystallization process, the colored bands will slowly form, from a white to gray, black and almost any color you can think of. The colors that you see come from the silica rich ground water, which is often mixed with other minerals such as iron oxide and magnesium.