Many minerals form beautiful crystals, but the most prized of all are gemstones. Uncut gems often look fairly ordinary–like rocks. It's only when they are cut and polished that they obtain the ...

However, it contains mercury, one of the most ... dangerous crystals and minerals remind us that not all of Earth’s treasures are as benign as they seem. While they may look beautiful and ...

"It was beautiful ... "You can hold most of the crystals on earth in the palm of your hand," says Jeffrey Post, a curator of minerals at the Smithsonian Institution. "To see crystals that are ...