The state of substances under ultrahigh pressures and temperatures (UHPHT) now raises a special interest as a matter existing under extreme conditions and as potential new material. Under laboratory conditions only small amounts of micrometer-sized matter are produced at a pressure up to 100 GPa and at room temperature. Simultaneous combination of ultrahigh pressures and temperatures in a lab still requires serious technological effort. Here we describe the composition and structure of the UHPHT vein-like impact glass discovered by us in 2015 on the territory of the Kara astrobleme (Russia) and compare its properties with impact glass from the Ries crater (Germany). A complex of structural and spectroscopic methods presents unusual high pressure marks of structural elements in 8-fold co-ordination that had been described earlier neither in synthetic nor natural glasses. The Kara natural UHPHT glasses being about 70 Ma old have well preserved initial structure, presenting some heterogeneity as a result of partial liquation and crystallization differentiation where an amorphous component is proposed to originate from low level polymerization. Homogeneous parts of the UHPHT glasses can be used to deepened fundamental investigation of a substance under extreme PT conditions and to technological studies for novel material creations.

High-pressure glass has attracted interest in terms of both its fundamental state under extreme conditions and its possible applications as an advanced material. in this context, natural impact glasses are of considerable interest because they are formed under ultrahigh-pressure and high-temperature (UHpHt) conditions in larger volumes than laboratory fabrication can produce. Studying the UHpHt glasses of the unique giant Kara astrobleme (Russia), we found that the specific geological position of the UHpHt melt glass veins points to an origin from a secondary ultrahigh-pressure (UHp) melt according to the characteristics of the host suevites, which suggest later bottom flow. Here, we propose a fundamentally novel model involving an upward-injected UHp melt complex with complicated multilevel and multi-process differentiation based on observations of the UHP silica glass, single-crystal coesite and related UHp smectite that crystallized from an impact-generated hydrous melt. this model proposes a secondary UHP crisis during the modification stage of the Kara crater formation. The results are very important for addressing fundamental problems in fields as diverse as condensed matter states under extreme pressure and temperature (pt) conditions, material and geological reconstructions of impact structures, water conditions in mineral substances under UHp conditions in the deep earth, and the duration and magnitude of the catastrophic effects of large asteroid impacts. The structure and properties of disordered substances have been studied for a long time and used in a wide range of applications. The behaviour of such substances under extreme conditions, including intense compression, is particularly interesting and is actively studied both theoretically and experimentally 1-7. High-pressure glasses have drawn interest both fundamentally as a material formed under extreme conditions and as a novel compound that could be used in new applications 8,9. The behaviour of disordered and weakly ordered systems under compression has been studied in microvolumes via diamond anvil. Typically, the compression process is performed at pressures of up to 100 GPa and sometimes higher. Furthermore, the experiments are typically performed at room temperature 1,4-6,9. Only a few experiments combining both high pressures and high temperatures have been carried out. However, such studies are intriguing because the simultaneous effects of temperature and pressure can produce profound internal changes in a substance. For example, SiO 2 glass has a significantly higher density and strength at a pressure of approximately 8 GPa and a temperature of 1100 °C than under cold compression 10. The most important properties expected from these glasses are the heat capacity, hardness, unusual optical properties and other physical properties, which can be used in high-tech materials and technologies, including high-energy lasers, microelectronics and innovative optics. Glasses with microstructural features at a nanoscale are potential basic matrices ...

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