in sedimentary rocks. History Ceylonite and pleonaste are historical terms in mineralogy. Nevertheless, both terms are used in the current mineralogical literature. References Ball, J.A., Murphy, S.T., Grimes, R.W., Bacorisen, D., Smith, R., Uberuaga, B.P., Sickafus, K.E., June 2008, Defect processes in MgAl2O4 spinel, Solid State Sciences, 10, 6, 717-724. Desa, M., Ramana, M.V., Ramprasad, T., 30 June 2006, Seafloor spreading magnetic anomalies south off Sri Lanka, Marine Geology, 229, 34, 227-240. King, R. J. (2004). Minerals explained 40: The spinels. Geology Today, 20(5), 194-200. Sickafus, K. E., Wills, J. M. and Grimes, N. W. (1999), Structure of Spinel. Journal of the American Ceramic Society. Skeen, George J.A. (1887) Journal of the Ceylon Branch of the Royal Asiatic Society, Volume IL-Part L No. 4, 97-98 Spinels, 1992, Physics and Chemistry of the Earth, 18, 105-125. Gemdat ceylonite Mindat ceylonite Mindat pleonaste Spinel gemstones