Some things that can indicate a chemical change are change of odor, change of color, change in temperature or energy, such as the production or loss of heat. An example could be the rusting of metal, there would be a color change of going from a shiny silver to a dirty, splotchy red color. Some things that indicate a physical change are change of appearance like change of shape, etc. It can also be like a change between a solid to liquid to gas. For example, the cutting of a piece of paper.
Aqua Auras belong to the Quartz family. It's a synthetic type of Quarts that was enhanced with the help of gold coating, and sometimes other materials. The reason why it's called as aqua is because of its distinctive blue color thanks to the procedure which made it.
Corresponding in size or amount to something else.