Description: Rainbow Agate 13mm x 18mm Rectangle Beads 9pcs approxSize: 13mm X 18mmShape: RectangleMaterial:Rainbow AgatePackaging: Strand (approx 9 pcs)What Is Rainbow Agate? Agate is a microcrystalline variety of quartz, chiefly Chalcedony, characterised by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks but can be common in certain metamorphic rocks.Description: Rainbow Agate 13mm x 18mm Rectangle Beads 9pcs approxSize: 13mm X 18mmShape: RectangleMaterial:Rainbow AgatePackaging: Strand (approx 9 pcs)What Is Rainbow Agate? Agate is a microcrystalline variety of quartz, chiefly Chalcedony, characterised by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks but can be common in certain metamorphic rocks.