Abalone is a mollusk found in warm seas that is well known because of its bowl like shell that is lined with highly iridescent nacre. Nacre, which is also known as mother-of-pearl, is the same substance that is found on the outer coating of pearls. The abalone shell lining varies in colour and can appear anywhere from a light grey to a deep blue. Many abalone shells can be said to be very reminiscent of the seas from which they are found. This is because the green-blue hues and brown-black lines found within the shell suggest the movement of the ocean waves.