By exploring mountains you will come across various mineable ores such as copper, gold or jade. To exploit them you will have to construct external buildings on hexes with them. From my experience as long as such resource is maximally within 2 hexes of your borders you will be able to do so. So I advice against settling closer than necessary (and aiming for having it in initial territory as it will lead to less of good farming space). You will be able to construct copper and gold pits from turn 1, while jade scrape will require Jade Working technology from Craft tree.
If you were wondering about what is the juicest here is some data:
- Gold Pit – cost 1200, income +40
- Gold Mine – cost 2500, income +120
- Deep gold Mine – cost 6000, income +220
- Copper Pit – cost 800, +20 income and produces copper for trade
- Copper Mine – cost 1500, +50 Income and produces more Copper for trade
- Deep Copper Mine – cost 3500, +100 income and produces the most Copper for trade
- Jade Scrape – Cost 1000, income +20, produces jade for trade
- Jade Quarry – Cost 2000, income +60, produces more jade for trade
- Deep Jade Mine – cost 4000, income +160, produces most jade for trade
We know that Jade is best for it’s trade value and Copper will outperform gold by mid/late game. I always thought people are over valuating gold because of that. But gold is still viable especially early/mid game as it is better in larger quantities than jade and copper (diminishing returns of trade when multiple sources are present). For level 2 of those buildings you will need Churn Drill technology in Craft (with Rammed Earth Wall from Power as prerequisite) and for final level Mine Ventilation from Warring States Era. Farming factions might consider getting ability to farm hills before going fully into such areas. Mining doesn’t require population and only suffers from Earthquakes as they may damage mines, which turns them off for few turns.
How to Mine Efficiently?
First of all realize that each external mining building is investment that will pay for itself after 30-70 turns. Don’t invest heavily in Copper and Jade if you don’t have trade network established already as it takes too long to pay for itself from income alone. When it comes to gold you can actually base your economy around it if you have 3+ sources of it. In theory it is most beneficial to spend money on highest possible level of Gold mine to squeeze the most income in given game span but in practice I would just go towards Gold Mines (more affordable) as cost of Deep Gold Mine is too high to swallow without stopping other expenses and it pays for itself in 60 turns. When setting up mining settlements remember that you want to build them as quickly as possible. Consider getting some unemployed pop or at least 10 pop total before stopping all other construction and focusing workers on mining. This way construction time will be minimal and you will start getting those benefits sooner. When it comes to Copper and Jade you should upgrade it asap and export it directly if possible (much higher profit this way) because caravansaries don’t care for mine level. If you have to re-export it to your cities consider doing It through waterborne trade and leave that mine at level 1. When it comes to corresponding technology priority I wouldn’t focus on them. Just research them when you have both 3-4 mines to upgrade and money to do so. As an income source it most likely won’t outperform farming but with good decisions it allows to snowball more and spend money towards future successes. So in short: several gold mines are a good base for mining industry early, alone copper vein is all you need to buff your trade and Jade should always be pursued and all economy strategies based around it (if available).