The continent of stability is a hypothesised large group of nuclides with masses greater than 300 daltons that is stable against radioactive decay, consisting of freely flowing up quarks and down quarks rather than up and down quarks bound into protons and neutrons. Matter containing these nuclides is termed up-down quark matter (udQM). The continent of stability is named in analogy with the island of stability. However, if it exists, the range of charge and mass will be much greater than in the island. Quark matter composed of up quarks and down quarks is predicted to be a lower energy state than that which contains strange quarks (strange quark matter), and also lower than the combination of quarks in the form of hadrons found in normal atomic nuclei if there are over 300 protons and neutrons. The lower limit of 300 was calculated based on a surface tension model, where the surface has a higher energy than the interior of the piece of quark matter. In order to be the absolutely more stable form, the energy must be lower than that of the most stable normal matter, that is 930 MeV per baryon. If these quark matter nuclides exist, they would be stable against fission, as fission would increase the surface. The quark matter nuclide could absorb neutrons resulting in an increase in its mass.