# Could humans dig out a 20km tunnel through quartzite by hand?

The dwarves in my world are humans who starting digging caves in the Maumturks and Twelve Bens in Ireland during the Iron Age, and eventually connected the caves via tunnels rather than trudge across the bogs that surround the hills. The rough timeline I have is that the caves start during the Iron Age, and by the 1500s the connecting tunnels are a well-established continuous network. Ignoring the fact that Iron Age humans would have very little reason to do this in the first place, I have the following problems:

1. The Maumturks and Twelve Bens are a mix of quartzite and granite, both of which are very hard rocks.
2. The length of the required tunnel network. For the sake of reference, here's a map that I've centred on the Maumturks (running from Leenaun down to Maum Cross, west of what's now the R336). The main network along the Maumturks would be approximately 20km long - and that doesn't include branch tunnels, or multiple levels going in the same direction.

So, could humans do this with hand tools, and if so, how long would it take?

• Compare to the pyramids of the Ancient Egypt. And they had only copper tools. May 28 '16 at 11:48
• First thought: "Owwww". Second: "oh, they can use tools...". English language, why must you be so confounding?
– Kys
May 31 '16 at 20:36
• @Kys "And if they ask you who I am, tell them I came the long way around" Aug 13 '18 at 22:01

Another approach is to ask how much volume a miner can remove per day. Let's take 1 cubic meter as a starting point. This is only possible since you've specified Iron Age mining. Roman tunneling in softer rock used bronze or copper tools, so their experience is not terribly applicable.

Assuming standard tunnel dimensions are 2 meters by 2 meters, with 2 miners working on the face at the same time, this will give a progress of 1/2 meter per day. 20 km will take 40,000 days, or about 109 years. Cut the average output by a factor of 3 and it still only takes about 330 years, which seems well within your time budget.

And, of course, you've missed a trick in overlooking motive: gold. Gold ore is commonly associated with quartzite, so following gold veins might well give some economic motivation to the miners.

ETA - My assumption of 1 cubic meter per day is, I grant, probably optimistic, which is why I added a second estimate of 1/3 that. There is undoubtedly historic information which can be used, specifically output rates for 19th century hard rock gold miners. I suspect that someone, somewhere, wrote about this at the time, but I'm unable to find such data with a cursory search. If anyone has access to that information, by all means present it.

Further edit - Gary Walker has pointed out that I mischaracterized Roman mining technology. Apparently I was wrong about iron tool use. My apologies. Take what conclusions from my mistake that you wish.

• I didn't know that about gold, so +1 for giving them a reason. May 29 '16 at 8:34
• To further lower the construction time the tunnels can be dug from both ends and/or from several secondary entry points on the way. This greatly increases the number of workers who can drive the advance simultaneously. May 31 '16 at 6:56
• Why do you say the Romans did not use iron tools in mining, iron was used for most tools according to Lynne Cohen Duncan May 31 '16 at 16:51
• @GaryWalker - Goodness. Well, it looks like I was mistaken. Not the first time in my life, either (I thought I was wrong, once, but I was mistaken.) I've edited. Thanks for the pointer. May 31 '16 at 17:14
• Each 1m of progress along a 2m×2m cross section is 2m×2m×1m=4㎥, at 1㎥/day this will give a progress of ¼ meter per day (not ½). i.e. all durations should be doubled. Jan 21 at 17:53

I say the answer is definitely yes.

The Romans built an even longer tunnel through rock, though not as hard as quartzite. The Gadara Aquaduct was probably an even larger engineering challenge given that the longest underground span was 106 km / 66 miles. This project took 120 years to complete.

Given dwarven miners, it would certainly take less than 120 years to complete.

EDIT. Actually I am assuming the average hardness of the rock was less, as this detail is not included in the article. Though granite is abundant in Palestine, it is almost certain some softer rock would be included in the rock excavated for the Gadara Aquaduct.

According to Mohs Scale of Mineral Hardness Quartzite has 100 absolute hardness, making it 1/16 as hard as diamond. The tunnel you want to build is about as long as The London Connection a 20 km tunnel through slowly permeable, seasonally wet, acid, loamy and clayey soils. This 3 meter wide tunnel took 3 years to build with modern tools in an easily diggable area. Now I'm assuming that your hand dug tunnel is as wide as a person. A simple amount of math implies that a tunnel of the same length but human size will take a year (plus 70-ish days) to dig with modern tools in the same area.

But you want tougher ground and simpler tools. Give or take clay is 6 times weaker than Quartz, being lower than 1 on the Mohs scale, so even with modern tools the tunnel will take 6 times longer (around 7.2 years). There is no solid math rule I can find for mechanical tools versus hand tools so I am going to assume that they are about 20 times weaker (heavy drills vs pickaxes, seems fair). This will give me around 52416 days or 144 years.

• The Mohs hardness scale runs from about 0 to about 10. Quartzite is around a 7.
– Joe
Aug 13 '18 at 23:58

The Incas dealt with stone by making small holes and filling them with flamable material. Once this was lit, rock would fragmentate, much like a glass full of hot water when you place it upon a very cold surface. This dispenses with explosives, but is a better technique than attacking very hard rock with only picks and axes.

• That's very interesting, but it doesn't really answer the questions asked here: "could they?" or "how long would it take?".
– Joe
Aug 14 '18 at 0:00
• The Egyptians drilled holes and hammered wood into them. The wood was then wet causing it to expand cracking the rock Aug 15 '18 at 0:50

Bashing away at quartzite is one helluva bitch. I'm a geology student and have tried doing that a few times with a sledge hammer and chisel and it can take dozens or even hundreds of swings to break off a fist sized piece of rock. Going at it with a pick axe would be a bit faster but still really slow. It's a completely different ballgame from digging in soft rock like this. https://www.youtube.com/watch?v=Uf6iqub5Lk8

But sounds like you're giving a couple thousand years to build this 20km tunnel so in that time frame it's do-able. My guess is with a pick axe it would take about 20 years per km. You would need to build ventilation shafts though at pretty regular intervals, and you could use those to work on the main tunnel at many different points simultaneously which would cut the time down from hundreds of years to tens of years or even less.

Still seems pretty pointless though, you'd be spending years to build the tunnel, not to mention a lot of labour building not only the main tunnel but ventilation shafts every 50 meters or so, and fixing/replacing thousands upon thousands of broken pick axes... The stone mined out would be difficult to shape for construction because it breaks into irregular shapes compared to other rocks and is very hard, and would probably come out in small pieces anyways. Quartz veins are a good rock to look for gold/minerals in but not quartzite which is one of the worst rocks to look for minerals in. They're made of similar material (quartz) but formed rather different, one is metamorphosed sandstone, the other is formed by hot underground fluids.

Realistically speaking it's definitely a lot more practical to just drain the bogs or build boardwalks over them.

You might consider the military tunnels during WWI in the Alps. Since it was difficult to attack up a mountain, the opposing armies would dig tunnels and fill them with explosives to blow the mountaintop positions away.

German-language source which claims 4 to 5.6 metres per day (more than one km per year) with the aid of some explosives.

• They don't have explosives... May 31 '16 at 4:57
• That's why I explicitly mentioned it. The distance per day has to be set in relation to the tools, and the wartime conditions.
– o.m.
May 31 '16 at 15:20