Even though it's an old topic I'll leave a comment on this; as an avid lamp-spectra enthusiast, I know quite a bit about lamp formulations.
ALL metal-halide lamps, ceramic or the classic type, including the xenon fired car headlights, contain mercury (Hg). It's an arc starter and a buffer. This is also why it's used in HPS lamps. Not used in low-pressure-sodium (neon is used).
Hg is the original ingredient (Clear Hg lamps from ~1935 to 1950), but over the decades, in order to BOTH increase the efficacy and CRI (color-rendering-index), other light-emmiting materials were added, such as phosphors on the envelopes or metal compounds in the arc tube.
Ceramic metal-halide lamps are essentially mercury lamps,.. but 60 years of added development! Remember that Hg spectra are simply emission line spectra (particularly in the UV). So the added phosphors and halides (Thallium, Sodium) and rare earth metals (dysprosium, holmium, thulium) account for the significant continuum radiation and added strong visible lines (like the sodium D-line ~589nm, in the deep yellow) leading to the high CRI AND greater (2x at least) efficacy.
So no-one or company will attemp to go backwards to create a CMV (ceramic mercury vapor) because it's already been done. Get a cheap diffraction grating (ebay) to identify the lamps. It's fun to look at all the variety of lamp spectra available on any modern city.