<p>Diatomite (diatomaceous earth) is a biogenic siliceous sedimentary material composed of fossilized diatom frustules, notable for its high porosity, low density, and structural regularity. This study provides a comprehensive synthesis of global diatomite geology, processing, and applications, emphasizing its growing role in sustainable and high-technology sectors. Major producing countries such as the United States, China, Denmark, Turkey, and France collectively account for over 80% of global production, serving industries ranging from filtration, absorbents, and construction to advanced nanocomposites and biomedical platforms. Geological factors, including volcanic influence, climate, and basin morphology, govern deposit quality and purity. Advances in beneficiation, surface modification, and functionalization have transformed diatomite from a traditional filter aid to a multifunctional biosilica used in water remediation, energy storage, and drug delivery systems. The study highlights challenges in resource sustainability, crystalline silica management, and standardization of biomedical-grade processing. Integrating life-cycle assessment, circular utilization, and biomimetic fabrication approaches will enable diatomite’s evolution into a strategic material for the green and biomedical industries.</p> Graphical Abstract <p></p>