According to this old thread, it isn’t aluminum. So gold? Perhaps ivory?
I think the double crown was more a style than a specific artifact. There were likely many of them made over the centuries, of a variety of materials.
The Deshret (red crown of Lower Egypt) was woven according to wikipedia
Several ancient representations indicate it was woven like a basket from plant fiber such as grass, straw, flax, palm leaf, or reed.
Regarding the Hedjet (white crown of Upper Egypt) it says:
Like the deshret, the hedjet may have been woven like a basket from plant fiber such as grass, straw, flax, palm leaf, or reed.
No example has been found
No examples have ever been found, but most speculation is that they were woven of plant fibres, like basketry, and possibly covered with fabric, leather or gold leaf.
I always figured that we would eventually dig up a tomb that had a set - though if they were woven they might have been ceremonially destroyed, or they were passed along to the next one.
Hm, was trying to remember if I knew anybody in the field over in Egypt, to ask them if they know about anything perhaps found at a dig that didn’t really get publicized. I mean, honestly back when they were digging Tut up they were more interested in all the gold and expensive bling they found, a woven wad of reeds would perhaps have been ignored or even tossed.