A 54-pound (25-kilogram) rock. Estimated auction price: $2 million to $4 million. Why so expensive? It’s the largest piece of ...

The Professional Numismatists Guild estimates the global rare coin market exceeds $10 billion in value. Over the past decade, rare coins have appreciated by 175%, outpacing the performance of many ...

Sotheby’s in New York is selling the 55-pound rock, named NWA 16788, for upwards of $1.6m, which it says is the largest piece of Mars on Earth. The reddish-brown Martian rock travelled 140 million ...