  We present radial velocities, Fe, and Al abundances for 180 red giant branch
(RGB) stars in the Galactic globular cluster Omega Centauri ($\omega$ Cen). The
majority of our data lie in the range 11.0$<$V$<$13.5, which covers the RGB
from about 1 mag. above the horizontal branch to the RGB tip. The selection
procedures are biased towards preferentially observing the more metal--poor and
luminous stars of $\omega$ Cen. Abundances were determined using equivalent
width measurements and spectrum synthesis analyses of moderate resolution
spectra (R$\approx$13,000) obtained with the Blanco 4m telescope and Hydra
multifiber spectrograph. Our results are in agreement with previous studies as
we find at least four different metallicity populations with [Fe/H]=--1.75,
--1.45, --1.05, and --0.75, with a full range of --2.20$\la$[Fe/H]$\la$--0.70.
[Al/Fe] ratios exhibit large star--to--star scatter for all populations, with
the more than 1.0 dex range of [Al/Fe] decreasing for stars more metal--rich
than [Fe/H]$\sim$--1.4. The minimum [Al/Fe] abundance observed for all
metallicity populations is [Al/Fe]$\sim$+0.15. The maximum abundance of log
$\epsilon$(Al) is reached for stars with [Fe/H]$\sim$--1.4 and does not
increase further with stellar metallicity. We interpret these results as
evidence for type II SNe providing the minimum [Al/Fe] ratio and a mass
spectrum of intermediate mass asymptotic giant branch stars causing the
majority of the [Al/Fe] scatter. These results seem to fit in the adopted
scheme that star formation occurred in $\omega$ Cen over $>$1 Gyr.
