Limestone has always been widely used in various sectors, thus having significant economic and environmental impacts. The quarrying process is, on the one hand, essential, but on the other, harmful to the environment and people’s health, therefore, the challenge is finding a balance. This review explores the multifaceted nature of limestone, a sedimentary rock predominantly composed of calcium carbonate. The formation of limestone, along with its various types and global occurrence, is discussed to provide a basic understanding. The diverse applications of limestone range from historical uses in ancient monuments to contemporary roles in cement production, plasticized polyvinyl chloride (PVC), and soda–lime glass. The discussion extends to post-mining solutions, showcasing successful rehabilitation and innovative repurposing of former quarries into useful infrastructures, wildlife habitats, and cultural spaces. This article draws attention to the importance of sustainable practices and technological developments to balance resource use with environmental conservation. Ultimately, it emphasizes the need for responsible limestone quarrying and proactive rehabilitation strategies to ensure that no permanent ecological problems will occur.

This letter describes how the temperature dependence of the electrical conductivity in semiconductors may be used to produce a linear floating molten zone which is intrinsically stable and uniform along its length. An analytical model and an experimental demonstration of such electric molten zone are both presented. This effect may be of particular interest for crystal growth and semiconductor recrystallization.

The limestone quarrying and processing industry generates huge amounts of waste, with limestone sludge being one of the most prevalent and challenging by-products. This study aims to evaluate the potential of limestone sludge as a sustainable secondary raw material for the mechanochemical synthesis of bioceramics, specifically hydroxyapatite (HA), for high-added-value applications in bone tissue engineering. High-energy milling is innovatively used as the processing route: dry sludge (functioning as the calcium source), a phosphate source, and water were milled with the aim of producing calcium phosphates (in particular, hydroxyapatite) via mechanosynthesis. The industrial sludge was thoroughly analyzed for chemical composition, heavy metals, and mineral phases to ensure suitability for biomedical applications. The mixture of reagents was tailored to comply with Ca/P = 1.67 molar ratio. Milling was carried out at room temperature; the milling velocity was 600 rpm, and milling time ranged from 5 to 650 min. Characterization by XRD, Raman spectroscopy, and SEM confirmed the progressive transformation of calcite into hydroxyapatite through a metastable DCPD intermediate, following logarithmic reaction kinetics. The resulting powders are fine, homogeneous, and phase-pure, demonstrating that mechanosynthesis provides a low-cost and environmentally friendly pathway to convert limestone waste into functional bioceramic materials. This suggests that Moleanos sludge is a viable and sustainable source to produce tailored calcium phosphates and confirms mechanosynthesis as a cost-effective and reliable technology to activate the low-kinetics chemical reactions in the CaCO₃-H₃PO₄–H₂O system. This work highlights a novel circular economy approach for the valorization of industrial limestone sludge, turning a difficult waste stream into a high-value, sustainable resource.