Minerals are typically formed when molten rock, or magma, cools ... comprised of aluminum oxide. The red color is caused by traces of chromium. Corundum also forms sapphire in many colors ...

A priest with a rock collection and a massive vision turned this corner of Iowa into a legend. The Grotto of the Redemption ...

The most colorful of all may just be rainbow obsidian, which features an array of iridescent colors, including shades of green, purple, and blue. Colorful, sure, but we’d say it reminds us more ...