Igneous rocks are classified according to their texture and composition. Composition refers to both the types of minerals within a rock and the overall chemical makeup of the rock (the two are obviously related). Texture refers to the size and arrangement of the minerals or grains that make up a rock.
Pentatonix (or PTX) is an American a cappella group consisting of five vocalists originating from Arlington, Texas.entatonix began with three friends who grew up together and were schoolmates at Martin High School in Arlington, Texas: Kirstin Kirstie Maldonado (born May 16, 1992), Mitch Grassi (born July 24, 1992), and Scott Hoying (born September 17, 1991).
Pentatonix is one of sixteen groups competing on season three of the Sing-Off on NBC. Group members include: Mitch Grassi, Scott Hoying, Avi Kaplan, Kirstin Maldonado and Kevin Olusola. They will make their debut Monday, September 26 on the Season Premiere: Part 2.