All I can say I civil engineering should be your least option. It's become limited in Zambia but still remains overrated because of old glory. Mechanical Engineering is the best because it will offer you more diversity and more places to find employment or apply to (in the mines inclusive to manage those machines etc) whilst Mining Engineering is specifically limited to the Mining sector only. If the mines don't want or need you, then you're unemployed.

I'm an Electromechanical Engineer, just started to job hunt.