In the Spanish and Portuguese wikipedias I found that Roraima was full of gold, uranium, thorium, cobalt, molybdenum, titanium, tantalum, columbite, cassiterite, diamonds and others. But the exploitation of the minerals didn't start until the 30s. The oldest and biggest production areas where:
- Serra do Tepequém
- Serra do Maturuca
- Serra Verde
- Vale do rio Cotingo
- Vale do rio Quinô Igarapé do Suapi
- Igarapé do Sapão
- Vale do rio Mau
- Água Fria
Unfortunately, I have been unable to find an economic map. Instead, I found a native map which shows a third of the state in hands of the Yanomami, The exploitation of that area didn't start until the 70s, so it shouldn't have nothing of value (Also, I think the Yanomami weren't conscripted).