  The z=4.591 quasar PC 1415+3408 exhibits very strong associated metal-line
absorption from the N V (1238,1242), Si IV (1393,1402), and C IV (1548,1550)
doublets spanning the velocity interval -1700 < v < 0 km/s. Also present, are
detached absorption troughs in N V and C IV spanning -5000 < v < -3000 km/s;
this is characteristic of broad absorption line (BAL) quasars, but the small
overall velocity spread suggests that PC 1415+3408 be classified as a Mini-BAL
quasar. The N V doublet is consistent with black saturation over the velocity
interval -1200 to -500 km/s; black N V absorption is extraordinary in all
classes of quasars at all redshifts. Over this velocity interval, the C IV
doublet is severely blended, but also consistent with black saturation. The
material over this range of velocity appears to fully occult the continuum
source, the broad emission line region, and any material that could give rise
to scattered light. In view of a unified scenario for BAL and Mini-BAL
absorption, these facts imply that the quasar is being viewed along a preferred
direction. On the other hand, the black Mini-BALs in PC 1415+3408 could be
explained if the BAL flow has an unusual geometry compared to the population of
BAL quasars, and/or the spatial extent of a scattering region is small at the
lower velocities (-1700 < v < 0 km/s).

Astrophysics