  The evolution of dust at redshifts z>9, and consequently the dust properties,
differs greatly from that in the local universe. In contrast to the local
universe, core collapse supernovae (CCSNe) are the only source of
thermally-condensed dust. Because of the low initial dust-to-gas mass ratio,
grain destruction rates are low, so that CCSNe are net producers of
interstellar dust. Galaxies with large initial gas mass or high mass infall
rate will therefore have a more rapid net rate of dust production comported to
galaxies with lower gas mass, even at the same star formation rate. The dust
composition is dominated by silicates, which exhibit a strong rise in the UV
opacity near the Lyman break. This "silicate-UV break" may be confused with the
Lyman break, resulting in a misidentification of a galaxies' photometric
redshift. In this paper we demonstrate these effects by analyzing the spectral
energy distribution (SED) of MACS1149-JD, a lensed galaxy at z=9.6. A potential
2mm counterpart of MACS1149-JD has been identified with GISMO. While additional
observations are required to corroborate this identification, we use this
possible association to illustrate the physical processes and the observational
effects of dust in the very high redshift universe.
