Positron annihilation in opals: Evidence of positronium formation

Natural opal samples have been studied with positron annihilation spectroscopy methods: Lifetime spectroscopy (LT) and Doppler Broadening (DB) spectroscopy. Additionally, samples have been examined by the Scanning Electron Microscope (SEM) and the BET method. The mean lifetimes and DB spectra shape of opals have been compared to other rocks by constructing the quotient spectra. Unusual properties of opals have been explained by positronium formation in the three-dimensional tektosilicate framework structure (SiO2*nH2O) of the opals.