What is commonly sold and known as white "turquoise" is actually a white magnesite. This creamy, white stone has either a brown or black matrix that resembles the patterns found in dry creek beds or crackled antique pottery. It can also be dyed dark shades of turquoise blue and green with stained deep black or brown matrix patterns, and sold as Tibetan "turquoise." This material can also be seen dyed orange, red and other colors.
White agate beads do exist and are available in various sizes and shapes.