MINERAL OF THE MONTH
June 2010 – Nantan Meteorite
A meteorite is a piece of a meteor that reaches the earth’s surface. Most of the meteorites found today were not witnessed when they fell. The Nantan meteorite fall is an exception. In May of 1516 during the reign of the Chinese Emperor Zhengde, the meteor hit the atmosphere above the Nantan province of China and broke into thousands of pieces that ranged in size from .35 ounces to 4,400 pounds. It is thought that the total weight of the meteor before it broke apart was around 20,900 pounds! The meteorite pieces were spread over an area that is approximately16 miles long and five miles wide.
A few years ago it was much easier to purchase Nantan meteorite specimens. Today they are very expensive costing around a dollar a gram. The one pictured below was acquired at the Denver Gem and Mineral Show around ten years ago. It weighs a little over one pound. Most of the Nantans that you see for sale are heavily oxidized. This is because large portions of the meteor was composed of iron oxide (rust) and not iron. By contrast this specimen came from the core of the meteor and is composed of approximately 98 percent metal. In addition to 92 percent iron and 6 percent nickel, more than ten minerals have been found in the Nantan meteorites including kamacite, taenite, plessite, scheribersite, triolite, graphite, spherlite, sideroferrite, dyslytite, cliftonite, and lawrencite. The Widmanstattern cross-banded woven pattern that is typical in iron meteorites is obvious in polished Nantan pieces.
What is interesting about these meteorites is that no one paid attention to them until 1958 when China needed a lot of steel to push the country a "Great Leap Forward". During this period, everyone was told to look for iron ore. Farmers knew about the iron rocks and had found that they were so pure that they could not be melted in a regular fire. They reported the specimens to the government and scientists were able to prove that the "iron ore rocks” were in fact iron meteorites.
P.S.—I didn’t realize until today that I featured Kentucky agate twice in the last few months as the selected mineral. Chalk it up to having too many things to do and not enough time to do them. I apologize for the duplication.
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