Alacrite is a family of cobalt-based alloys. One member of the family, XSH Alacrite, also known as L605, is described as "a non-magnetic, stainless super-alloy whose high surface hardness enables one to achieve a mirror quality polish".[1] It was "originally developed for use in aircraft." [2] Another use is in drug-eluting stents.
The Institut National de Métrologie in France uses one-kilogram cylinders of XSH Alacrite as "secondary mass standards". This particular alloy is composed primarily of cobalt, with the remaining elements being 20% chromium, 15% tungsten, 10% nickel and 0.1% carbon. Its density is 9150 kg/m3.[2]