Crystal System...

Like all Obsidian, the Aqua Blue variety is amorphous and is in the mineral class of silica oxides. It is formed from volcanic flows when lava that was rich in silicic acids was cooled very quickly (flowed into a lake or the ocean). The result of this creates a mass that is very rich in minerals, and sometimes has small gas inclusions. Obsidian can not technically be classified as a crystal as it was cooled too quickly to form crystal lattices like many other stones we use for healing.

Its coloring ranges from a deep aqua to a paler aqua shade. Much of today's obsidian has come from Mexico and this variety is identified by its unique aqua blue color. Variations in the oxidation state of the small amounts of Iron, Beryllium, and/or Aluminium Silicate contained in its mix is what provides its lovely hue.

It should be noted that much of the brighter colored obsidians (blues, greens, some  reds and yellows) in the market place have been re-formed by man through a heating process turning them into smoother tumbled shapes for easier handling. While perhaps not as zippy, energetically speaking after their reform, they still contain all the goodness built in from their original creation. So, a bit slower acting over a longer period of time.