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Comment by dalke | Hacker News Reader

Most of the iron in the crust is bound in silicate or carbonate minerals, and energetically expensive to extract.

FWIW, the Kiruna orebody is the biggest known continuous body of iron ore in the world, 4 km wide, 80 meters thick on average, and of unknown length. See https://www.lkab.com/en/Future/Urban-Transformations/Why/Wha... .

Or quoting from http://www.mining-technology.com/projects/kiruna/ :

> Since mining began at the site over 100 years ago, Luossavaara-Kiirunavaara AB (LKAB) has produced over 950Mt of ore, yet only one third of the original ore body has been extracted.

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Also, the iron ore in Kiruna is magnetite, and particularly rich in iron. This allows the iron to be extracted using magnets rather then the chemicals needed for hematite, the more abundant cousin of magnetite. Also, the trains used to transport the iron pellets to the coast for sea transport use very little energy, due to the regenerative braking used during the loaded trip down to sea level.

The part about trains sound really interesting. Do you mean that the energy gained through regenerative braking while a loaded train moves downhill is enough to move an empty train back up the mountain?

If so, how do they store the energy? Do the trains carry massive batteries, or do they draw power from (and contribute back to) the grid?

http://en.wikipedia.org/wiki/Iore - "From Riksgränsen on the national border to the Port of Narvik, the trains use only a fifth of the power they regenerate. The regenerated energy is sufficient to power the empty trains back up to the national border."

It's pumped into the grid.

Wow, like those funicular railways where one car acts as the counterweight for the other.

And where the passengers only want to ride it from the top to the bottom.

True. Oddly enough, I've been hiking in regions that were ski resorts during the winter, and they sometimes ran the chair lifts during the summer. We'd use them for hiking. There were some published hikes that involved lifts, buses, trains, etc. Perhaps out of a sense of sportsmanship, we tended to ride down, but never up.

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