For many years after aluminium was discovered in 1827, it was treated as a precious metal, as the process of extracting it from the ore Bauxite was so costly. Castellani’s use of the metal for the blade in this ornamental dagger, adorning it with gold and precious stones, provides a clear indication of quite how highly prized aluminium was during the mid-19th Century.
It was not until H. Saint-Claire Deville developed a process for producing aluminium industrially in 1854 that the value of the metal started to drop; from 3,000 francs per kilogramme in 1855 to 375 francs per kilogramme a year later.
For a comparable example see Munn, G.C. Castellani and Giuliano, London, 1984, p164 plate 172.