wood!

Early rails: A wooden balanced incline used for gold mining, at the Illinois Mine in the Pahranagat Mining District, Nevada in 1871. An ore car would ride on parallel tracks connected to a pulley wheel at the top of tracks

Read more: http://www.dailymail.co.uk/news/article-2149899/The-American-West-youve-seen-Amazing-19th-century-pictures-landscape-chartered-time.html#ixzz1xI0FiAni

Whilst the ideal material for rails is steel, there's no reason why, in the right circumstances (financial, resource availability, loadings) wood can't be used. This is a shot from an American wooden railway of the 1870s, used to transport ore.

And not just wood! Granite was used on the Haytor Granite Tramway on Dartmoor, sourced along the route, the route being used to transport granite to the coast.

The dystopia lot like to dishearten us by asking how even railways will survive Peak Oil because of the accompanying resource shortages - hopefully the above might shut 'em up a bit!