Shock compression of finely ground CaF2 crystals embedded into graphite powder in cylindrical recovery ampoules was found to yield single white crystals of 0.1mm in size within the Mach cone, where the developed temperatures/pressures are exeedingly high. The composition of these crystals CaO3SiO2SiC is a result of chemical interactions of mixture and SiO2 due to cumulative eruption of Si from steel walls of ampoules and its reaction with O2 from sample pores. The atomic structure of crystals was characterized by IR spectroscopy and XRD. The formation of relatively large single crystals can take place only in the melted unloaded material.