  We present observations of the most radio-luminous BAL quasar known,
1624+3758, at redshift z = 3.377. The quasar has several unusual properties:
(1) The FeII UV191 1787-A emission line is very prominent. (2) The BAL trough
(BALnicity index 2990 km/s) is detached by 21000 km/s and extends to velocity v
= -29000 km/s. There are additional intrinsic absorbers at -1900 and -2800
km/s. (3) The radio rotation measure of the quasar, 18350 rad/m^2, is the
second-highest known.
  The radio luminosity is P(1.4GHz) = 4.3 x 10^27 W/Hz (H0 = 50 km/s/Mpc, q0 =
0.5), radio loudness R* = 260. The radio source is compact (<~ 2.8 kpc) and the
radio spectrum is GHz-peaked, consistent with it being relatively young. The
width of the CIV emission line, in conjunction with the total optical
luminosity, implies black-hole mass ~ 10^9 M(sun), L/L(Eddington) ~ 2. The high
Eddington ratio, and the radio-loudness, place this quasar in one corner of
Boroson's (2002) 2-component scheme for the classification of AGN, implying a
very high accretion rate, and this may account for some of the unusual observed
properties.
  A complex mini-BAL absorber at v = -3000 km/s is detected in each of CIV, NV
and OVI. The blue and red components of the CIV doublet happen to be unblended,
allowing both the covering factor and optical depth to be determined as a
function of velocity. Variation of covering factor with velocity dominates the
form of the mini-BAL...
