It surprised me to see calcium-48 classed with nickel-56 as a doubly magic nuclide with a long half-life, as was stated in Physics Today (August 2010, page 16). The half-life of 56 Ni is only 6 days, while that of 48Ca is given by the Brookhaven National Laboratory webpage http://www.nndc.bnl.gov/chart as 2 × 1019 years.
Calcium-48 has been considered stable, at least until the mid 1990s. The nuclide is so neutron rich that even the small amount present in cosmic materials is a problem for schemes of nucleosynthesis. 1 Nevertheless, Fiorella Castelli and Swetlana Hubrig were able to identify the nuclide in the spectra of chemically peculiar stars 2 because of the large isotope shift of lines of the Ca II infrared triplet. Varying isotopic ratios of 48Ca may be found in chemically peculiar stars, and in a few cases, the isotope shifts are compatible with the Ca being pure or very nearly pure 48Ca. 3