Gaia Stone is a green glass supposedly made from ash from Mount Saint Helens
Now I did have some Ash from the inital eruption because My fathers work place was well coated with it and my Ceramics Instructor did use some in a galze which was indeed green but the vast majority of current Gaia stone probably has been colored and may not really have much genuine material from Mount Saint Helens.
I find that most of the warnings about obsidian are rather overblown.
At least one famous Crystal author had a strong reaction to it and most of the warnings, fear, loathing ,etc. stem from that source. There was an inference in some of the material written about obsidian that those of particularly high and pure spiritual quality would be subject to this effect. So perhaps that is why I have lived much of my life near mountains of the stuff and have had a large obsidian sphere in my front room for over a decade with only benificial effects.
Obsidian reveals the hidden .grounding, protecting,. Obsidian is used in pouches and grids to help bring on visions and psychic insight but the most well known way of working with obsidian for divination is the scrying mirror. The scrying mirror a usually convex surface ideally made of polished black obsidian is gazed into/ upon while one seeks to receive visions or information about issues, the future, a present situation or to foretell events , discover hidden knowledge , prophecy, or perception by intuition and instinctive foresight.