Turquoise is an opaque mineral that occurs in beautiful shades of blue, bluish green, green, and yellowish green. Most of the world’s turquoise rough is currently produced in the southwestern United States, China, Chile, Egypt, Iran, and Mexico. Very few minerals have a colour that is so well known, so characteristic, and so impressive that the name of the mineral becomes so commonly used. Turquoise is the birthstone for the month of December.