Final answer:
The Meteor Crater near Flagstaff was formed by an iron meteorite, evidenced by a fragment of the meteorite and its classification as an 'iron', which is mostly metallic nickel-iron and extraterrestrial in origin.
Step-by-step explanation:
We can be sure the meteorite that formed the Meteor Crater near Flagstaff was composed of iron by examining the evidence left behind from the impact and the nature of meteorites. One of the key evidence is a fragment from the iron meteorite itself that was responsible for the formation of Meteor Crater in Arizona. Furthermore, meteorites are traditionally placed into three broad classes: irons, stones, and stony irons. The irons are nearly pure metallic nickel-iron and are the most obviously extraterrestrial because of their metallic content. Since pure iron rarely occurs naturally on Earth and is found as oxides or mineral ores, finding a chunk of metallic iron strongly suggests an extraterrestrial origin. Additionally, a piece of the Allende carbonaceous meteorite has inclusions that may date back to before the formation of the solar nebula, implying that such meteorites can originate from far beyond Earth.