Scientists recently examined a silver ring holding a gem engraved with the word “Allah” that was discovered in a Viking-era woman’s grave by Swedish archaeologists in the late nineteenth century. The team used a scanning electron microscope to determine that the gem, thought to be an amethyst, is actually colored glass, which would have been an exotic material in the Viking world. They also discovered that the ring is still in mint condition, with no sign of wear. “That means it was not an heirloom passed from person to person that randomly ended up in Scandinavia,” says Stockholm University biophysicist Sebastian Wärmländer, who led the team. “The ring was brought here soon after it was made, and corroborates ancient tales about direct contact between Viking Age Scandinavia and the Islamic world.”

A new dating technique is making it easier for paleoanthropologists to study the human evolutionary record by making it possible to date a wider range of stones and sediments. A team of scientists, including Darryl Granger of Purdue University, has looked to aluminum-26 and beryllium-10, isotopes that are created when rocks are out in the open, exposed to cosmic rays. Once the rocks are buried, the isotopes no longer form, and then begin to decay at known rates. Ultrasensitive instruments that can measure the tiny amounts of these isotopes can tell scientists how long a rock has been underground. Granger used this technique on quartz crystals from South Africa’s Sterkfontein Cave that surrounded the skeletal remains of an early hominin dubbed “Little Foot,” formally known as Australopithecus prometheus. Granger dated the skeleton at 3.67 million years old. The results are controversial because they show that A. prometheus lived at the same time as the human ancestor A. afarensis, which raises questions about the relationship between these species.

Powerful empires throughout history have exploited precious resources, but this extraction can take a toll on the environment. Researchers have recently discovered two examples of imperial mining efforts—separated by hundreds of years and thousands of miles—that left behind pollution that can still be measured today.

When the Mongols conquered China and founded the Yuan Dynasty (A.D. 1271–1368), they established an ambitious silver mining operation near Lake Erhai in Yunnan Province. Production grew rapidly, and by 1328 almost half of the national tax revenue came from silver mined and processed there. Once ore containing silver was mined, it was heated to release impurities such as lead. A recent analysis of sediment cores from Lake Erhai found that lead pollution spiked during the Yuan Dynasty, peaking at three to four times the level caused by modern mining. This surprisingly high level of ancient pollution may be due more to the inefficiency of the refining process than to the amount of silver mined, says Aubrey Hillman, a doctoral candidate in geology at the University of Pittsburgh.

Preindustrial lead pollution due to silver mining has also been found in South America, where the traces show up in a core sample from the Quelccaya Ice Cap, high in the Peruvian Andes. The Incas pioneered silver extraction in the area, but it wasn’t until Spanish colonizers dramatically ramped up production in the sixteenth century that lead was released in quantities large enough to be detected almost five hundred years later by a team led by geoscientist Paolo Gabrielli of The Ohio State University. The Spanish increased the amount of ore mined by using forced Inca labor, and introduced a more efficient refining process in which ore was pulverized, releasing lead-laden dust into the atmosphere. The ore was then mixed with liquid mercury to remove impurities. Taken together, these discoveries provide ample evidence that mineral wealth and pollution have long traveled hand in hand.