I don't even know if they are called helicopter leaves really.
When I was making moulds the other day, I pressed some of those leaves in the mould. That way, the back side of the mould is not going to waste. I found these leaves in a park in Portugal when I was visiting Kerrin from Sigmosaics last year so I thought it was cool to see them in pressed in porcelain.
I made a little hole on top of the leaf and hope that Anna from LilaRubyKing will find a way to turn these into a neat jewellery design sometime...