Talk:Snowflake Obsidian/@comment-44445435-20191216153703/@comment-34997073-20191217020759

a large amount of earths crust is made out of silicon and oxygen which is largely what quartz is composed of(and other trace elements such as iron for amethysts-which peridot said was present in the area). so what types of gems can be produced on a planet is likely dependant on composition rather than environment(such as blue's kyanite colony-which is usually in aluminum rich rock)