Impactites are terrestrial rocks that have been impacted by asteroids or comets. Following such events, earth rock is melted, shattered or shocked. At times even new minerals are formed as a result of these high-pressure events such as microdiamonds. Impactite may be found on or beneath the floor of the crater, in the rim, or in ejecta (material launched from the crater following an impact). As might be imagined, impact craters are identified as a result of the presence of impactite, as well as other diagnostic impact products such as shatter cones, impact glass and other chemical and isotopic evidence.

The specimen of Popigai is from Popigai Crater in Siberia, which at 100 km in diameter makes it among the largest on Earth. It formed about 35 million years ago in a collision that was so energetic that it produced what is now the world’s largest diamond deposit. Gardnos originates from Norway’s 5-km-diameter Gardnos Crater, a smaller event that is believed to have occurred approximately 500 million years ago. A nature preserve named Meteorite Park has been established in the Gardnos Crater region. The 24-km-diameter Nördlinger-Ries Crater in western Bavaria was the result of an impact that occurred about 14 million years ago. Within the actual depression is the town of Nördlingen and the Ries Crater Museum. The Ries impact event is also believed to be the source of moldavite, a beautiful impact glass found in the Czech Republic, which implies molten glass having been splashed a distance of hundreds of miles. Most impact craters were once thought to have been volcanic in origin; scientists have today documented 190 impact craters on Earth.

Christie's would like to thank Dr. Alan E. Rubin at the Institute of Geophysics and Planetary Physics, University of California, Los Angeles for his assistance in preparing this catalog note.