My first encounter with emery, was when I was younger, with emery boards for shaping nails, but emery was in use much earlier. In fact, there are emery pouches surviving from the end of the nineteenth century!
Emery is a very hard rock type used to make abrasive powder. It is black or dark grey in colour, and comes in various grades. Crushed or naturally eroded emery (known as black sand) is used as an abrasive — for example, on an emery board, as a traction enhancer in asphalt and tarmac mixtures, or as used in mechanical engineering as emery cloth. The finer grade emery is the best for sharpening needles.
Where does emery come from? The Greek island of Naxos used to be the main source. It has been mined on the eastern side of Naxos for well over two thousand years until recent times.
The way to use an emery strawberry, is to pass the needle straight through, from one side to the other so that any tiny rough burrs were pushed back parallel with the needle so they wouldn't become a bother when the needle was used. The other advantage of using an emery was that the powder cleaned skin oils from the needle, keeping it clean, shiny and rust-free.
To be able to use an emery correctly, you need something small. Now I know why the lady ordered two, this was the only place she could find small emeries and I am glad to have been able to have help, no matter how unwittingly!