About 3 kinds of major mining methods in ancient Chinese mine (Actually modern mine still used these naming method).
Vertical shaft + galleries
Inclined shaft + galleries
level shaft (adit) + "blind shaft"
A mine uses the combination of all these three techniques to form a complex. And the dark area is where the targeted minerals deposit/vain.
And Aeruginous Mountain ancient mine (or Copper Green Mountain, or Tonglushan as direct verbal transcription) is a massive mine with surface area discovered so far 2km x 1km. And it dug deep below local water table. With hundreds of different kind of shafts. The later period at B.C.E. in ancient Hang Dynasty is about the same time as Roman Republic, the earliest one can date back to 12 century B.C. in Shang Dynasty. And it particularly mentions about the solution of water gathering with trenches on the floor of galleries and gather them using gravity to a blind shaft or simple dead end vertical shaft as a filling shaft. And it used some techniques to solve the air ventilation problem. (Something about different natural air pressure. I do not quite understand the details). The depth of a vertical shaft can go as deep as 60 meter, and several vertical shafts with many galleries surrounding and connecting them can form a connected system. (I am curious about how they were able to connect different vertical shafts underground. Some impressive engineering.)
Some video to demonstrate some of the structure I mentioned. But it's in Chinese.
http://elearning.npm.gov.tw/courses/digital_2-4-1/course10/10_2b_0.htmhttp://elearning.npm.gov.tw/courses/digital_2-4-1/course10/I roughly translate the 10_2b_0 section. At the beginning of the film, there is purple flowers at the foreground it's called copper grass flower grows where mineral is rich. And the description said, copper ore can be found at shallow depth, so it's easy to strip mind in open field. When the shallow mineral deplete then dug deeper shafts into the earth. And it's the picture of the ancient mine (Tonglushan) on the surface with strip mine.
Second picture : 2 to 3 thousands years ago (where the ancient mine was activate), these shafts used premade supporting structure (made of wood) to ensure safety. And wooden mechanics devices (pulley etc.) were found to help transporting the ore. Then the animation of one of the reconstructed shafts complex structure.
Third : After the ores were mined, miners broke them down into small chucks on site before transport. And they use water flow and gravity to select heavy mineral from dusts and useless rock. And the devices they used. (It's can be used to determine if certain location has rich or poor mineral. it is also part of the system to control underground water flow).