Hmmm! She tries again a few more times, sometimes holding the coin down with a finger and sometimes starting with her hand cupped over it so it's not already touching her but can't go flying.

It's definitely way easier to put way more magic into the metal if she's touching it. How much it moves still depends on the amount of magic, not touch.

The metal seems to do nothing for a little while as magic builds, and then go flying when some critical point is reached.

She wonders if this means she could fly better on a metal broom than a wooden one. Can she put magic into the coin, almost but not quite enough to make to go flying, and then leave it there for a little while, and then put the last bit in?

Ceasing to supply magic makes it move with however much it currently has, even if it's below the point where it'd start moving by itself.

Ooh, that'll be helpful for fine control. Can she get it to lift into the air slowly by adding a bunch of tiny pulses of magic with pauses between?

It falls fast enough that it doesn't seem possible to 'stop' enough to trigger it, and then start and stop again before it hits the ground.

If she magics it until it goes flying, can she track it well enough to put more magic in it before it lands, or is it too fast?

She can do that if she's fast enough! It's actually weirdly easy to track its motion through the air, with the metal-sense.

That is So. Much. Fun. She plays around with it for a while, seeing how long she can keep it in the air, trying to control the trajectory, doing it all again with her eyes shut and going off metal-sense alone.

It's slightly trickier, like that. It's like the metal-sense was guiding her eyes more than anything else. She can't as easily get a sufficient sense of where the coin is moment to moment to put magic into it, without vision.

If it works best in concert with her eyes she'll keep them open. Can she get anywhere on telling what the properties she made up words for mean, or would she need more examples?

More examples would definitely help, at any rate. The coin does not confirm nor deny her guesses.

Then she'll go stand near her father's work area, examining the metal parts of his tools, and the shoes he puts on horses, and any metal bits in the horses' tack, looking for patterns.

Most of the iron is pretty similar. There are a lot of smaller differences between iron and copper... Some of the iron items feel subtly different from each other. A couple of the big tools, specifically.

And when she feels a glimpse of silver in a well-off customer's pocket, the silver is pretty similar to the copper, with a few differences, but even higher on one of the two things copper has a lot of.

The next time her father is between tasks, she points out the points out the subtly different big tools and asks what makes them different from the rest. She's already chattered excitedly about her special magic to him earlier, so it's pretty clear why she's asking. 

Maybe the blacksmith who made them does large tools in a different way, and that affects the metal?

Maybe! Unfortunately the smith who made them doesn't live in this town, so she can't ask. Maybe the local smith will know, but she wants to save up a bunch of questions and then ask him all of them at once. She sits down with the coin again and starts trying to tell if she can do anything other than sense it and push magic into it in the way that makes it move.

She can push magic in slightly different spots and  directions. If it's unbalanced it sets the coin spinning wildly as well as flying into the air.

Getting any sort of fine control here is tricky! She goes back to working with really small amounts of magic, trying to get the coin to scoot along the floor instead of flying up in the air.

This is doable with some practice!

She spends a lot of time practicing over the next several days, basically whenever she isn't eating or sleeping or busy helping her parents around the house. Eventually she gets the coin to scoot around in circles or triangles or whatever way she wants. After a week she takes all the small metal things she can find and goes to the local smith, intending to wait for a quiet moment and ask him some questions.

The local smith has plenty of quiet moments - most of his work is simple and low-demand, here.

"I've seen you poking around with magicked metal, niña. No wonder you're curious about metalworking. Come on in."

She smiles as she enters the workshop. "I'd like to know what makes one piece of iron, or copper, or anything different from another piece. I can sense that there's more to metal than what kind it is and how it's shaped, but I don't know what I'm sensing."

"Well there's different ways of smithing. I know the most about iron, iron's useful. Wrought iron's just taken out of the ground and beaten into shape. Forged iron's been melted. I can't forge with what I have here."

"Is forged iron better somehow, to make people go to the trouble? Or is it that you can make it take more shapes that way?"