# A Comprehensive Review on Mine Tailings as a Raw Material in the Alkali Activation Process
## 2 Mineralogy of Mine Tailings  
The mineralogy of mine tailings can vary widely depending on the type of ore being mined, the processing methods used, and the geological characteristics of the deposit [43]. The mineral phases in mine tailings can be categorized into two main groups: primary phases (reacted and unreacted) and secondary phases (precipitated and weathered). These distinctions are crucial for understanding the mineralogical evolution of mine tailings and their potential environmental impact, as shown in Figure 1. Unreacted primary phases are the mineral phases that originally existed in the ore or rock being mined [44]. These minerals remain largely unchanged during the milling and processing of the ore. Examples include quartz, feldspar, and primary sulfide minerals like pyrite, chalcopyrite, and sphalerite. Reacted primary phases are mineral phases that have undergone some degree of alteration or reaction during the mining and milling process, such as sulfide minerals that may oxidize to form secondary sulfate minerals like jarosite or goethite due to air and water exposure [45]. During precipitated secondary phases, these secondary mineral phases form after the deposition of tailings into the environment. They often result from chemical reactions between tailings, water, and other environmental factors. Examples include the precipitation of iron or aluminum hydroxides (e.g., ferrihydrite and gibbsite) due to changes in pH conditions. Furthermore, weathered secondary phases can alter tailings over time. For example, exposure to rainwater and temperature fluctuations can lead to the leaching of soluble components, the transformation of minerals, and the formation of new weathering products, like clay minerals or iron oxides. The comprehensive characterization of fresh and weathered mine tailings materials is essential for thoroughly understanding their material properties and behavior. In order to develop an effective waste management plan, it is essential to study the mineralogy, chemical composition, and potential behavior of the tailings under various environmental conditions [47]. The chemical compositions of various mine tailings are demonstrated in Table 1.  
The variability in the elemental composition of mine tailings from different mining sites presents a significant challenge for their standardized use in the construction industry. A multifaceted approach can be implemented to address this issue by focusing on characterization, classification, treatment, and regulatory guidelines. X-ray fluorescence (XRF) and X-ray diffraction (XRD) tests could be conducted to determine the exact composition of the tailings. Developing a classification system based on the chemical and physical properties of tailings can categorize them into different types, each suitable for specific construction applications. In some cases, thermal treatments can alter the physical and chemical properties of tailings, making them more suitable for use in construction. Regulatory guidelines and standards for using mine tailings in construction will help to ensure their safety and performance. By implementing these strategies, the variability in the elemental composition of mine tailings can be managed, allowing for their standardized and safe use in construction applications. Minerals are fundamental components of the Earth's crust, and they play a vital role in geological processes, the formation of rocks, and the development of natural resources. They are naturally occurring, inorganic solids that possess specific chemical compositions and atomic arrangements, leading to unique crystal structures. Figure 1: Health and environmental impacts of mine tailings [46]. In the Earth's crust, minerals are classified into four major classes based on their chemical composition [66].