Howlite is a calcium silicoborate that is naturally white, often with a dark gray or black spider-web matrix. Howlite is commonly dyed to imitate turquoise and lapis lazuli. Howlite turquoise is a popular substitute for the real thing. North America is the world's primary source of howlite. Beadaholique.com carries howlite beads in many shapes, from basic rounds to sweet stars.