By embedding all element samples in clear acrylic, they are beautifully presented and also protected from tarnishing. This format also helps to addresses health and safety issues, as all potentially toxic or corrosive substances are permanently encased in a thick layer of robust resin. Argon gas and mineral oil is further used to ampoule reactive samples and preserve their freshly cut appearance.
And even though it’s a noble gas and not reactive, the Ar sample is sealed in Argon, too.
via way of the woo