Pamela-
   I think that the "brick dust" is uric acid crystals.  Very common in hte
first few days of life.  Very serious sign of kidney failure in adults, but
not so with newborns in the first few days.  But beyond day 3-5, usually a
sign of dehydration and need to make sure to FEED the BABY one way or
another.  Once fluids increase, usually continue to see the crystals for
about 24 hours, then no more.  I'm sure others will post more technical info.
   Debi Ferrarello, RN, IBCLC