  We model the mineralogy and distribution of dust around the white dwarf
G29-39 using the infrared spectrum from 1-35 microns and combining a wide range
of materials based on spectral studies of comets and debris disks. In order of
their contribution to the mid-infrared emission, the most abundant minerals for
G29-38 are amorphous carbon, amorphous and crystalline silicates, water ice,
and metal sulfides. The amorphous C can be equivalently replaced by other
materials (like metallic Fe) with featureless infrared spectra. The
best-fitting crystalline silicate is Fe-rich pyroxene. In order to absorb
enough starlight to power the observed emission, the disk must either be much
thinner than the stellar radius (so that it can be heated from above and below)
or it must have an opening angle wider than 2 degrees. A `moderately optically
thick' torus model with mass 2x10^19 g fits the spectrum well. A physically
thin (less than the white dwarf radius) and optically thick disk can contribute
to the near-infrared continuum only; such a disk cannot explain the
longer-wavelength continuum or strong silicate features. The silicate
composition contains minerals found from cometary spectra and meteorites, but
Fe-rich pyroxene is more abundant than enstatite (Mg-rich pyroxene) or
forsterite (Mg-rich olivine) in G29-38, in contrast to what is found in most
comet or meteorite mineralogies. Enstatite meteorites may be the most similar
solar system materials to the G29-38 dust. Finally, we suggest the surviving
core of a `hot jupiter' as an alternative (neither cometary nor asteroidal)
origin for the debris, though further theoretical work is needed to determine
if this hypothesis is viable.
