The Raman spectra of a series of related minerals of the pinakiolité group have been collected and the spectra related to the mineral structure. These minerals are based upon an isolated BO33− ion. The site symmetry is reduced from D3h to C1. Intense Raman bands are observed for the minerals takeuchiité, pinakiolité, fredrikssonité and azoproité at 1084, 1086, 1086 and 1086 cm−1. These bands are assigned to the ν1 BO33− symmetric stretching mode. Low-intensity Raman bands are observed for the minerals at 1345, 1748; 1435, 1748; 1435, 1750; and 1436, 1749 cm−1, respectively. One probable assignment is to ν3 BO33− antisymmetric stretching mode. Intense Raman bands of the studied minerals at 712 cm−1 are attributed to the ν2 out-of-plane bending mode. Importantly, through the comparison of the Raman spectra, the molecular structure of borate minerals with ill-defined structures can be obtained. Copyright © 2010 John Wiley & Sons, Ltd.