Reprint of Genesis of halloysite from the weathering of muscovite: Insights from microscopic observations of a weathered granite in the Gaoling Area, Jingdezhen, China

Halloysite is a 1:1 clay mineral typically derived from the hydrothermal alteration of alumina-silicate minerals such as biotite and feldspar. In this paper, microscopic observations are used to describe the formation of halloysite on weathered muscovite plates from a granite outcrop near Gaoling village, Jingdezhen, eastern China, where kaolinite was first discovered approximately 1000 years ago. X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR) analyses are used to identify halloysite, while field emission scanning electron microscopic (FESEM) observations reveal two types of halloysite that have different shapes and spatial distributions around muscovite. Most of the halloysite is present as long filaments with a uniform occurrence and is found on both the exposed (001) surfaces and edges of muscovite. In contrast, a small amount of the halloysite-like mineral occurs as stumpy, sheet stacking, which has an irregular appearance and occurs mainly at the margins of the muscovite plates. It is proposed that the halloysite was derived from the surface leaching of muscovite by two possible mechanisms: dissolution-precipitation or local dissolution-rearrangement of residue structure. Interestingly, similar phenomena were also found in historic tailings at Gaoling village, which most likely suggests a short-term process of formation for the nano-sized halloysite. (C) 2015 Elsevier B.V. All rights reserved.