No, they were political as well, the reason, or better said the guise, was to "civilize the natives" and partially get them western comfort(which was also mostly a guise although it did give them hospitals).

It was also a bit of a way to show other European colonizing nations Belgium didn't want to lose the pissing contest.

The "civilization" excuse served as to not show an obvious systematic suppression and genocide and to gain support from other European nations. They all more or less worked with this principle for colonisation. This circlejerk kept the colonies stable and suppressed for a while

The first few years were centered around precious metals and natural resources (not minerals, petroleum or rubber).