Magnesium minerals are important for understanding the concept of geosequestration. One method of studying the hydrated hydroxy magnesium carbonate minerals is through vibrational spectroscopy. A combination of Raman and infrared spectroscopy has been used to study the mineral hydromagnesite. An intense band is observed at 1121 cm−1, attributed to the CO32−ν1 symmetric stretching mode. A series of infrared bands at 1387, 1413 and 1474 cm−1 are assigned to the CO32−ν3 antisymmetric stretching modes. The CO32−ν3 antisymmetric stretching vibrations are extremely weak in the Raman spectrum and are observed at 1404, 1451, 1490 and 1520 cm−1. A series of Raman bands at 708, 716, 728 and 758 cm−1 are assigned to the CO32−ν2 in-plane bending mode. The Raman spectrum in the OH stretching region is characterized by bands at 3416, 3516 and 3447 cm−1. In the infrared spectrum, a broad band is found at 2940 cm−1, which is assigned to water stretching vibrations. Infrared bands at 3430, 3446, 3511, 2648 and 3685 cm−1 are attributed to MgOH stretching modes. Copyright © 2011 John Wiley & Sons, Ltd.