👉 Icosteus is a term that refers to a type of rock, typically found in the northern regions of the world. It is composed primarily of quartz and other minerals and can be found in various geological formations such as sedimentary rocks, volcanic rocks, and metamorphic rocks. The term "icosteus" comes from Greek and means "stone of the mountain," which suggests that it is a rock with a distinctive appearance due to its location on the summit of a high mountain.