A spark-induced hot gas jet of a gas turbine combustor igniter has been investigated using high-speed schlieren, stereo, and stereoscopic shadowgraph imaging visualization techniques. The schlieren images show that the spark-induced local high pressure generates a spherical shockwave. The energy released by the spark initiation combines with the igniter tip geometry to produce a hot gas jet. The hot gas front velocity was obtained from the high-speed schlieren images. The results have shown that the input voltage does not have much effect on the propagation speed of the hot gas front. It was observed that each spark had caused the erosion of some melted tiny metal bits flying off the igniter tip. The 3D velocity vectors of the flying off metal bits are calculated by a stereo reconstruction and evaluation algorithm. It has been found that the amount and velocity distributions of the eroded metal bits are very different even at a fixed input voltage to the igniter, which contrasts with the quite consistent hot gas jet development. The 3D structures of the interaction boundary between hot gas and ambient air are reconstructed for the first time using a stereoscopic shadowgraph technique.