Help tutorial. Can't mine. "Must designate impassable mineable rocks."

[Kidcharlemagne]

Just started and I'm about a minute into tutorial and have followed it exactly.  It's now telling me I'll want to mine some minerals.  There is a piece of steel slag outlined and with an arrow pointing to it.  I select "mine" and get the pickaxe icon but when I click on, or attempt to drag select, I get a"must designate impassable mineable rocks.". I've not played around with anything and have only clicked what tutorial told me.  What the hell am I doing wrong?

[Canute]

A steel slag is a remain from some destroyed structure.
You can't mine this, you can smelt it later.
You need to look at he mountain/hills there you can find steel ore.
Select one steel ore, then click on the mine button.
Or select from the architect menu the mine button and then you can designate the steel ore for mining.
After that you should check at the work tab that some colonist are assigned to mining, or noone would go there and mine.

[Hoshi]

Yeah, that steel slag is an item on the ground. It's something you pick up and smelt to make steel, one way of getting steel in the game.

The other would be the way the tutorial wants you obtain the steel, which is to mine it out of the walls of a hill somewhere. You can mine those. Natural rocky wall surfaces are the only things you can mine.