Mine! Mine! Picking the Mind of a Geologist

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Luckily I had a geologist up my sleeve when creating the story of a dragon snoozing in a copper mine. A friend of mine with a degree in geology had worked in a geology-based field. I plied her with coffee and wheedled her secrets from her!

The technology in this story correlates to roughly what existed in the 11th to 13th century. A portion of the tale occurs in a volcano turned mountain containing natural copper veins.

Q: Could the mountain have a forest on it?
If yes, what is the minimum span that would need to occur for conditions to have a dense forest at least at the base of the mountain?

A: Yes – Depends on the rest of the composition of the mountain. Standard mountains where copper exists requires hundreds to thousands of years for a luscious forest to form.

The trees would be mostly coniferous trees; Douglas firs, hemlocks, cedars, and pines.

Q: Could there still be warmth, even slight warmth in the mountain.
If so, how far down?

A: Yes – at least 9km miles down (the crust is 10km thick at the ocean) if the cavern is at sea level.

Q: Could natural copper exist in this mountain?
If not, is there a metal that could?

A: Yes, it can. Copper can form in volcanic mountains depending on how the mountain is created. If the mountain is like the volcanoes on the west coast – intrusive (inside) magma deposits – you can find copper and other minerals) in vein deposits. The veins form when the rocks in the middle of the mountains break because of various pressures (happens naturally) and those cracks and spaces fill with the deposits of your choice (depends on the chemistry of the lava). This kind of extraction requires a mine like you are talking about to be created to go into the mountain and receive it. They did this a long time ago, so your timeline works as well. I would recommend you use this type of “rock building.”


Another way copper deposits can form is through basaltic lava flows – extrusive (outside of the volcano). This volcano would be similar to the Hawaii Island volcanoes. The lava is rich in all sorts of minerals, but they are TINY. In the cooling process, similar mineral structures grow around each other but in smaller deposits. The way to gather these deposits is through open pit mining and then melt them down to extract all of the minerals separately (this is based on my VERY limited knowledge of mining PS).

Q: What gem could exist here too?

A: With the intrusive way of mining – yes. You can get gold, iron, silver, and lots of gems (emeralds [mineral name: Beryl], rubies and sapphires, but not diamonds though – those are a special kind of gem).

Q: I picked obsidian because it looked like it could work, but I’m happy with any gem.

A: Obsidian requires extrusive volcanoes as it’s volcanic glass that cools rapidly. Obsidian deposits form in the layers of basaltic flows over hundreds of thousands of years that volcanoes erupt. Its harder to get other types of mineral deposits with extrusive deposits.

Iron is VERY commonly found with copper and gold if you are going for accuracy
Copper prefers to bond with itself and other minerals.

Q: Could the metal and gem both be found in the same large cavern?

A: Yes because the chemical makeup of the magma is ever changing as is slowly cools.
One additional note was that the metals would be on the surface of the cavern, but the gems would be inside the walls.

Q: Were wooden beams used to reinforce mine shafts during the period where my story takes place?

A: I’m not sure – I want to say yes as it was how the Egyptians kept their small spaces open while they were building tombs and that was a LONG time before the time frame of your story.

Q: Would it be possible for the dragon to cause a cave-in of the tunnel he used to get into the large cavern to make it so people wouldn’t easily find him?

A: Yes, it just depends on how broken up the rock is structurally.

Q: How would he cause the cave-in?

A: He’s clumsy and disturbs the precariously positioned rocks that have already been broken up over the natural pressures. It’s known as “rotten” mountains.

Q: How would he undo it when he wanted to leave?

A: Good question – usually you can’t. I would recommend having two release tubes/venting shafts. One the dragon can destroy and the secondary being a “secret” one that people don’t know exists.

Q: Is there a more straightforward way to ensure his privacy while he hibernates that hasn’t occurred to me?

A: Secret secondary vent shaft thing that the humans never found.

Additional Information

  • The presence of water is necessary for all of this to happen.
  • At some point up the side of the mountain, the vegetation will cease to grow making a sharp demarcation line.
  • Three different ways to form mountains
    • Intrusive made by lava flows – big crystal structures, granite, explosive eruptions
    • Extrusive are lava flows on lava flows – Hawaiian islands there are rocks – won’t have crystals
    • Rocks smashed together – Himalayas pressurized metamorphosed granite, not mined; except for countertops.

One of the things she geeked out about was the how copper changes to glossy, bubbly shapes called popcorn when heated and cooled in its veins. I told her about basic dragon first aid and its heating element.

Thank you Julie for taking the time to explain rocks to me.


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