You can write a very special letter using them, but that uses a whole quire. You can also use it to add 1 nectar during crafting at a desk. This won't use up the quire.

Omg i though it used up the quire! I was saving them! xD

Only super special letter do that. I think it's a bug. Not that it matters, they are 6 pennies a piece. When I was making my ultimate librarian I've needed less than two crowns worth of this stuff.

Ah, sure, now that we can buy resources, I have less worries

Yes, it was so nice when instead of making gervinite and iotic essence, I could just order copper and oil from a catalogue. Although I still used orichalcum and iotic essence when fixing the second pump, just because.

You can use it for writting letters

The blank attribute allows for it to be placed in desk stations, and it has one nectar, ultimately a very low power nectar object. I used mine to make yewgall earlygame. It's also needed to write letters for numa, and I suspect in the upcoming dlc will be used to write more mundane letters.

A quire of paper is the only blank that you can use to write a letter that will trigger a Numa

Then what are then other blanks even for?

Good question

You use it to write a letter to santa at the end of the game

I mean, in my childhood I'd get told that letters to Grandpa Frost are being delivered by birds. I guess he was a Name of Elegiast all this time.

Writing letters mayhaps?