  We announce the discovery of SST-Lup3-1, a very low mass star close to the
brown dwarf boundary in Lupus III with a circum(sub)stellar disk, discovered by
the `Cores to Disks' Spitzer Legacy Program from mid-, near-infrared and
optical data, with very conspicuous crystalline silicate features in its
spectrum. It is the first of such objects with a full 5 to 35 micron spectrum
taken with the IRS and it shows strong 10 and 20 micron silicate features with
high feature to continuum ratios and clear crystalline features out to 33
micron. The dust in the disk upper layer has a crystalline silicate grain
fraction between 15% and 33%, depending on the assumed dust continuum. The
availability of the full Spitzer infrared spectrum allows an analysis of the
dust composition as a function of temperature and position in the disk. The hot
(~ 300 K) dust responsible for the 10 micron feature consists of a roughly
equal mix of small (~ 0.1 micron) and large (~ 1.5 micron) grains, whereas the
cold (~ 70 K) dust responsible for the longer wavelength silicate features
contains primarily large grains (> 1 micron). Since the cold dust emission
arises from deeper layers in the inner (< 3 AU) disk as well as from the
surface layers of the outer (3-5 AU) disk, this provides direct evidence for
combined grain growth and settling in the disk. The inferred crystalline mass
fractions in the two components are comparable. Since only the inner 0.02 AU of
the disk is warm enough to anneal the amorphous silicate grains, even the
lowest fraction of 15% of crystalline material requires either very efficient
mixing or other formation mechanisms.
