Weird needle like crystals formed in galvanic cell after drying

So I set up a series of galvanic cells for fun; had a brass nut in a glass container and a chunk of zinc in another. I immersed the brass nut and zinc in a solution of saltwater, and connected them with a saltwater-soaked paper towel.


When the side with the brass dried out, a bunch of salt crystals, as well as blue copper carbonate formed. However, a bunch of long, white, needle-like crystals also formed. What could these be?


