Christian Lacroix’s “Gold-Gotha” ensemble and reliquary cross boasts a riot of gemstones. It’s on display at the Metropolitan Museum of Art in New York until October. Others are often clear. Quartz, ...

While investigating hackmanite, a natural wonder material, researchers found that it, in addition to two other minerals, can change their color upon exposure to UV radiation repeatedly without wearing ...

While investigating hackmanite, researchers found that it can change color upon exposure to UV radiation repeatedly without wearing out. The results show that the inexpensive hackmanite, which is easy ...

Identifying minerals blends careful observation with dependable tests that reveal each specimen’s unique signature. Geologists examine hardness, streak, luster, cleavage, and crystal habit to tell ...