|The glass shown in A, B (B: the field is 14 mm wide) is coating a sandstone exposed in the central uplift of the Rubielos de la Cérida impact structure. The glass has a greenish to whitisch color and is transparent to milky. In thin section (C, D (xx nicols) – the field is 6 mm wide), the sandstone shows heavily damaged, and intense cataclastic flow texture is observed to merge with the glass. Quartz grains are strongly fractured and show multiple sets of planar fractures (PFs) and planar deformation features (PDFs).|
|Interpretation: Despite the occurrence of shock features in the sandstone, the glass probably did not form by shock melting. We suggest frictional melting by extreme dynamic metamorphism in the impact event (excavation or – more probably – modification stage when the uplift formed) and the glass to be pseudotachylite. Temperatures in excess of 2,000 °C were probably required for the homogenization of this glass (David Griscom, pers. com.).
The location of this spectacular exposure of the glass-bearing sandstone remains secret for the moment in order to prevent it from destruction by rock hunters.