Specimen Notes from the Mini Museum: Libyan Desert Glass
Dec 23rd, 2015
In the southeastern spur of North Africa’s Great Sand Sea, there are several fields of luminous, yellow-green glass known as Libyan Desert Glass (LDG). Due to the lack of any visible impact crater, the most likely source is a low-density asteroid or comet airburst explosion leading to the fusion of silica-rich sands roughly 28,500,000 years ago.
The distribution of Libyan Desert Glass across several sites leads some scientists to speculate that there may have been multiple explosions, though recent surveys of the surrounding watershed provide stronger evidence for distribution by erosion.
While the dunes of the Great Sand Sea may seem timeless, during the Early to Middle Paleolithic Era the region was often home to a wetter climate capable of supporting playa wetlands. Further to the south, in what is now one of the least hospitable places on earth, permanent lakes and savanna grasslands supported an even greater abundance of life.
Throughout the region, there is plentiful evidence of multiple periods of early human settlement. Coming and going as the climate changed, our ancestors shaped the glass into tools and decorative items, but paleolithic cultures are not the only ones to use the glass.
When English archeologist Howard Carter catalogued the tomb of King Tutankhamen in 1922, he identified the scarab at the center of this pectoral as chalcedony, a naturally occurring silica formation. Seventy-five years later, a chance viewing by an Italian mineralogist named Vincenzo de Michele led to studies which revealed the material to be Libyan Desert Glass.
This 18th Dynasty find is unique among the gems of ancient Egypt, as it is the only known use of Libyan Glass. The scarab is part of a twofold representation of the sun-god, which in Egyptian mythology could be represented by both scarab and falcon.
In addition to the translucent color of the scarab in King Tutankhamen’s burial pectoral, Libyan Desert Glass also comes in much darker colors.
The specimen in the Mini Museum comes from several fragments of Libyan Desert Glass, including the large chunk pictured above and the lighter fragments pictured below.
The silica content of Libyan Desert Glass is nearly 98%. Fused silica glass this pure is commonly used in high temperature applications, and is very resistant to weathering. It also happens to be very clear. The color of the recovered fragments indicate concentrations of olivine, orthopyroxene, and rare earth elements.
Preparing the Libyan Desert Glass for inclusion is a delicate process, as the shards can be quite sharp. After several stages of reduction with precision glass cutters, specimens are carefully reviewed for size and shape.
The glass is quite pure so I wasn’t sure how it would look in the acrylic, but I’m really excited about the way this specimen turned out!
Now, it’s back to work!
Hans Fex, Creator and Chief Curator for the Mini Museum