  The Apollo 15 & 16 missions were the first to explore the Lunar surface
chemistry by investigating about 10% of the Lunar surface using a remote
sensing X-ray fluorescence spectrometer experiment. The data obtained have been
extensively used to study Lunar formation history and geological evolution. In
this work, a re-evaluation of the Apollo 15 & 16 X-ray fluorescence experiment
is conducted with the aim of obtaining up-to-date empirical values for aluminum
(Al) and magnesium (Mg) concentrations relative to silicon (Si) of the upper
Lunar surface. An updated instrument response, a newly reconstructed Lunar
trajectory orbit, and improved intensity ratio calculations were used to obtain
new intensity ratio maps. The resulting Lunar Al/Si and Mg/Al X-ray maps show a
clear distinction in Lunar mare and highland regions. The mean Al/Si and Mg/Al
intensity ratios for the mare regions obtained from the newly obtained maps are
0.54$\pm$0.07 and 0.54$\pm$0.17, respectively; for the highland regions, the
values are 0.76$\pm$0.07 and 1.07$\pm$0.13, respectively. For the Mg/Si
intensity ratio, no clear distinction between Lunar features is obtained and we
derived a mean value of 0.47$\pm$0.13. Our determined intensity ratios are
lower than previously published. These values can be used to infer
concentration ratios when accounting for Solar activity, inter-orbit
variability, and measurements from different instruments. We employed a
correction to infer concentration ratios by comparing our intensity ratios
directly to Lunar rock concentrations obtained from various Lunar missions.
