My google news page has burst forth the news that metallic hydrogen has been produced in a laboratory using a diamond anvil cell. Only one service mentions (at this particular moment) that it has been called into question at - at least - premature. That can be read about in Nature: Physicists doubt bold report of metallic hydrogen
Here I only want to ask about the evidence. Is it only the sudden change in visual appearance change as recorded in a camera on top of the microscope, at a specific temperature and pressure? That it "looks shiny?" Or is there actually more direct data than that?
note: I am not asking if the data is sufficient or not, nor if it is convincing, or metallic or not. Just a narrowly defined question about the extent of the observations that have lead to the proposal that a metallic state was achieved.
above: potentially three states of hydrogen as viewed in a diamond anvil cell, from here.