Limonite is an important ore of the gossan-type gold deposit and the iron deposit; nevertheless, the microstructure of limonite has not been investigated in detail. For the purpose of probing into morphological characteristics and microstructures of limonite ore, the authors investigated 70 samples from the Xinqiao sulfide iron deposit using X-Ray Powder Diffraction (XRD) and Scanning Electron Microscope (SEM). The limonite ore can be divided into two groups based upon the components and microstructures. Limonite (Ⅰ) with honeycomb structure was mainly sourced from the weathering of pyrite ore. The major minerals identified are represented by goethite with a minor amount of hematite and quartz. The particle sizes of goethite is in the range of 500 nm~2 μm with a higher ratio of length/diameter. Limonite (Ⅱ) with kidney structure was derived from the weathering of siderite ore. Goethite is also the major mineral, and the secondary minerals include manganite, hematite and illite. The length of goethite is less than 500 nm, with a lower ratio of length/width. The information on the mineralogy and microstructure of limonite not only can be used to infer the type of the primary minera but also is of important indicating signicance in search for gold deposits in gossans.