A rare rhodochrosite gemstone discovered decades ago in Colorado’s now-closed Sweet Home Mine could sell for thousands of dollars in an October auction.

ALBUQUERQUE, N.M. (KRQE) — It’s a “hydrated phosphate of copper,” but you may just know it as turquoise. The blue-green mineral widely regarded as a gemstone has significant deposits ...

Diamonds, rubies, emeralds, and sapphires are most of the classic gemstones adorning royal jewels. But they used to be accompanied by a stone that nowadays is most often found in museum ...