A lot of posts (including, I fear, some of mine) have been working on the assumption that there is no iron in the crust if this planet. I even surmised that the lack of a moon might have prevented the dense elements from being stirred up into the crust. However, Mars' satellites are a fairly feeble excuse for moons, especially in tidal terms, and its surface is practically wall to wall rust, so, at a guess, based on the fact that iron's the low point on the nuclear energy curve, any rocky planet's going to have ferrous compounds in its crust.
But they needn't be the simple oxides, sulphides and sulphates common on Earth, which can easily be reduced using charcoal, generated from trees, solar energy and CO2 (or more recently coke, sort of delayed action charcoal). After all, there's more aluminium than iron in the Earth's crust, and that wasn't extracted until the nineteenth century. If iron were tied up in some more stable compound, not extractable by easily achievable heat we could go on having red blood but not be able to smelt iron ore into the pure metal (or the rather carbon-rich mixture that ultimately gives us steel)". No, I can't think of a ferrous compound that would do this, but I'm no chemist. I do think that if it was as universal as that, as against the diversity of ferrous (and ferric) compounds on Earth, it's probably some biological process converting all available iron into this, probably a bacterium.
