Abundance
Neodymium is a relatively rare element, but is one of the most abundant rare earth elements. Its abundance is measured in parts-per-million (ppm), which is a measurement used to describe the concentrations of a specific element, compound or ion in a solution. In this case, it refers to the concentration of Neodymium in the earth’s crust and in its oceans. According to Jefferson Lab’s web-page on Neodymium, its estimated crustal abundance, or abundance in the earth’s crust, is about 41.5 milligrams per kilogram or 41.5 ppm. Also, the Jefferson Lab web-page also projects that its estimated oceanic abundance is about 2.810-6milligrams per milligrams per liter or 2.8×10^-6 ppm. This abundance of Neodymium is slightly less than the crustal abundance of copper and zinc that measure at about 60 milligrams per kilogram or ppm, and 70 milligrams per kilogram (ppm) respectively.