Mace is the bright red lattice that wraps around the nutmeg seed inside the fruit. It is peeled away by hand, pressed flat and dried until it turns deep amber.
Because only a few grams come from each fruit, mace has always cost considerably more than the seed it protects. It is used more sparingly and it is worth the difference.
Where nutmeg is sweet and heavy, mace is brighter, more delicate and more perfumed, with a clear citrus edge. Cooks who use both tend to reach for mace when the dish is pale or refined and nutmeg when it is rich.
Sold as whole blades rather than ground, so the oil stays sealed inside the blade until the moment you use it.