Glass failure analysis expert witness performs a failure analysis on a tempered glass window. The failure was initiated by a nickel sulfide, NiS particle. The glass failure analysis expert was able to retrieve both halves of the failure origin. One side of the failure origin contained the protruding NiS particle. On the other side of the failure origin there was a hole out of which the NiS particle had pulled out when the two halves of the failure origin were separated. Above are two photographs of the two halves of the failure origin retrieved during the failure analysis. These photomicrographs were taken at 100X magnification using Nomarski interference contrast optics. This is a manufacturing defect. The NiS entered the glass during the melting operation.