Answer to Question 1
When iron meteorites are sliced open, polished, and etched with acid, they reveal regular bands called Widmansttten patterns. Those patterns are caused by certain alloys of iron and nickel that formed crystals as the molten metal cooled and solidified long ago. The size and shape of the bands indicate that the molten metal cooled very slowly, no faster than 20 degrees Kelvin per million years. The rate of cooling give scientists clues to the origin of meteorites.
Answer to Question 2
Iron meteorites make up 66 percent of finds but only 6 percent of falls. One of the best places to look for meteorites is in parts of Antarctica because Earth rocks are buried deep beneath the ice cap. Antarctic ice sheets flow outward and meteorites concentrate in areas where the ice runs into mountain barriers and evaporates. Teams of scientists have found a thousand meteorites in a single two-month expedition, and over 40,000 after 25 years of work.
Why iron meteorites? Because an iron meteorite doesn't look like an ordinary rock, they are recognizably different. Stony meteorites deteriorate rapidly when exposed to weather; irons are made of stronger material and generally survive longer, therefore easier to spot on the ground. The fact that only 6 percent of falls are irons shows that iron meteoroids, although easier to find on Earth, are relatively rare in space.
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