I don't see a staring electrode or a quartz arc tube. Unless your referring to the vague resemblance?Looks like the old style mercury vapour lamps ?
Many of the older electricians will be familiur with them !
Ceramic metal halides fail in strange ways. Ive seen some develop a hole in the arc tube where the gases leak out and the lamp turns brown.Definitely metal halide, had the correct ballast too. We were just amazed at how the internals crystallized like that. Not sure what caused it.