Silvery, white metal that becomes yellowish in contact with air .
In nature, neodymium is found in the Earth's crust, 24-40 ppm, in minerals such as monazite, bastnaesite, gadolinite and cerite, of which the first two are the commercially important sources . The isotopes found in nature are 142Nd (27.13 %, stable), 143Nd (12.18 %, stable), 144Nd (23.80 %, T½ = 2.1 · 1015 years), 145Nd (8.30 %, stable), 146Nd (17.19 %, stable), 148Nd (5.76 %, stable) and 150Nd (5.64 %, stable) .
In pure solid form, neodymium exist in the following forms:
α-form: hexagonal crystal at < 868 °C 
β-form: body-centered cubic crystal at > 868 °C