A type of glass that is tinted blue because of industrial processes or man-made additives is referred to as blue obsidian. The name gives it a ring like it is found in a jewelers shop. It is true that blue-tinted volcanic glass occurs naturally, it is rare and easy to make synthetically. It still looks great in jewelry when it is polished or cast to look like a crystal formation.
The color blue suggests water, the ocean, and a calm personality. Other blue minerals have been considered semi-precious since ancient times. The association between blue gems and wealth or scarcity gives this fairly cheap material extra clout in the faux gem industry. It does look great on a ring or on a chain. If unrefined, it can resemble raw quarried stone even if it is a byproduct of cleaning other minerals. It is sought after by amateur jewelry makers because it is easy to make great results with it.