Researchers have used various methods to identify the materials and techniques employed by mosaic artists in Late Antiquity. As the Roman Empire began to decline and global trade routes collapsed, craftspeople were forced to find creative ways to acquire the expensive raw materials used in colorful mosaics, which often had to be imported. A recent study involved chemical analysis of a sample of 19 tesserae—the individual pieces used in mosaics—from 1,600-year-old mosaics discovered at a villa in Halicarnassus, in what is now Turkey, to determine what materials the mosaicists used and how they were made. The luxurious estate, which belonged to a man named Charidemos, was built in the fifth century A.D. and its floors were decorated with centuries-old themes from Greek and Roman literature and mythology.

The analysis revealed that, of the 19 tesserae examined, 11 were made of stone, seven from glass, and one was ceramic. Researchers were surprised to learn that six of the seven glass pieces were crafted from recycled glass. “Since new tesserae simply could not be bought for money,” says University of Southern Denmark archaeometrist Kaare Lund Rasmussen, “it’s possible that local workshops began specializing in recycling old glass into the bright new colors sought after by rich landowners.” To see an additional photo of the mosaic, click here.

The largest assemblage of extremely rare worked Neolithic rock crystal was uncovered by archaeologists from the University of Manchester at the monumental complex of Dorstone Hill in Herefordshire, England. More than 330 fragments of crystal were discovered during excavations at the nearly 6,000-year-old complex, which once featured a series of long earthen mounds and large timber buildings. Rock crystal is a form of nearly transparent quartz that was coveted by Neolithic people, who likely believed it had magical properties. “In the Neolithic period, there was no glass—or any other transparent solid material—so rock crystal would have been a really distinctive and notably different material,” says University of Manchester archaeologist Nick Overton. “Quartz crystals do a few really unusual things with light. They can be used to split white light into the visible spectrum and they are also triboluminescent, which means they emit a flash of light when struck with another stone or crystal.”

The exotic mineral was likely transported to Herefordshire intact from a source between 80 and 100 miles away in Wales. Archaeologists do not believe that the rock crystal was ever fashioned into finished tools. Instead, they suggest that the knapping process was an important part of the early Neolithic community’s identity. The crystal fragments were collected and deposited into cremation pits containing human remains and other stone tools as a way of commemorating the dead.

For years, Gulf Shores, Alabama, resident Harry King has tried to raise awareness of what locals call Indian Ditch. King was sure that this now largely obscured mile-long waterway was an ancient canoe canal that linked Mobile Bay with the Gulf of Mexico. University of South Alabama archaeologist Gregory A. Waselkov had always assumed the canal was a nineteenth-century earthworks, but was finally persuaded by King to lead a study of the site. “When I saw the scale of the remaining sections of canal, I was blown away,” says Waselkov. “It is so impressive.” Excavations of a surviving canal berm yielded charcoal samples showing that the earthworks were surprisingly old, dating to about A.D. 600. Waselkov’s team’s analysis of the local water table and sediments from the canal suggest that it was probably traversed during cold weather months and was likely dammed at either end. “Despite the old folk name of Indian Ditch, the canal was not a simple, sea-level ditch dug across the peninsula, but a sophisticated, engineered feature,” says Waselkov. He and his team hope to work with Native cultural specialists to explore the possible spiritual and symbolic dimensions of the waterway. To see an archival photo of the canal, click here.