Yeah, they are just students (in what, who knows?), so I have no doubt that it is not the most accurate resource in the world. But it gives a pretty good general account. A more in depth study would take a lot longer, and of course give better results.
Little things like; "Interestingly, an iron pillar dating to 400 A.D., remains standing today in Delhi, India. Corrosion to the pillar has been minimal a skill lost to current ironworkers. Iron is rarely found in its native state the only known sources being Greenland where the iron occurs as nodules in basalt that erupted through beds of coal and two very rare nickel-iron alloys." (
http://neon.mems.cmu.edu/cramb/Processing/history.html) Are, to me, quite interesting.
But yeah, if you want more information then the generalizations they give, they do give references and these references are the place to look if you want better info then an overview.
That is, of course, if you are interested in such things.
P.S. Stuff like "Malachite, a green friable stone, was the source of copper in the early smelters. " might add to the game, but it might also make it to 'bulky'. So, yeah.
P.P.S Yeah, it definitely seems that NONE of these websites were written by English Majors... There are so many grammatical errors in them that it isn't funny. -..-