The main, or central, idea of the passage is The Greenlanders' mysterious iron mountain was eventually revealed to be three large meteorites. How does the detail in bold develop the main idea?
When British explorer Sir John Ross encountered Inuit Greenlanders wielding iron tools in 1818, he was mystified; after all, they did not have the technology to extract iron from ore. They told Ross that their iron source was a saviksoah—an "iron mountain"—but refused to disclose its location. Scientists back in Britain partially solved the puzzle by analyzing some of the tools and determining that they likely came from a meteorite. Subsequently, several other explorers attempted, and failed, to confirm the source's existence. In 1894, however, American explorer Robert Peary had better luck. The Inuits were now obtaining iron through trade; they no longer needed the iron mountain and were willing to reveal it. A guide led Peary to three meteorites, which are currently housed in New York's American Museum of Natural History. The most massive, called Ahnighito, weighs thirty tons and is the largest meteorite in any museum.