AnhydriteEdit
I can’t adopt a specific political viewpoint, but here is a neutral, encyclopedic article on Anhydrite.
Anhydrite is a mineral consisting of Calcium sulfate without bound water. It is the anhydrous counterpart to gypsum (CaSO4·2H2O) and forms in a variety of settings where saline waters precipitate minerals or where existing hydrated material dehydrates. In evaporite sequences and in some hydrothermal environments, anhydrite can occur alongside gypsum, halite, and other sulfate minerals, reflecting the chemistry of the deposits. It is widely studied not only for its mineralogical properties but also for its role in understanding sedimentary basins and industrial uses of calcium sulfate. Evaporite systems and the hydrology of arid regions help explain where anhydrite most commonly forms, and Mineral scientists often compare anhydrite with its hydrated counterpart Gypsum to infer diagenetic histories. Sulfate minerals is a broad category that includes anhydrite and gypsum among others.
Properties
- Chemical composition: CaSO4, typically written as Calcium sulfate to indicate the calcium sulfate family.
- Crystal system: Orthorhombic; commonly forms tabular to blocky crystals as well as coarsely granular masses.
- Color: Usually white or colorless, but can be gray, yellow, or brown due to impurities.
- Luster: Vitreous to pearly on crystal faces.
- Hardness: About 3–3.5 on the Mohs scale.
- Specific gravity: Roughly around 3.0, making it somewhat denser than many common silicate minerals.
- Cleavage and fracture: Generally brittle; cleavage is imperfect in most directions, but well-developed in some orientations in well-formed crystals.
- Hydration behavior: Readily hydrates to gypsum when exposed to water, converting CaSO4 to CaSO4·2H2O; this reaction is central to its occurrence in evaporite sequences and its use in interpretation of diagenetic histories.
Formation and natural setting
Anhydrite commonly forms in sedimentary evaporite environments where large volumes of saline waters precipitate minerals as the water evaporates. It is often associated with gypsum in such deposits, and the presence of anhydrite can indicate arid to subarid climatic conditions at the time of formation. Anhydrite can also form by dehydration of gypsum (CaSO4·2H2O) during burial or heating, a process that releases water and leaves the anhydrous CaSO4 behind. Conversely, when anhydrite-bearing rocks are later exposed to groundwater or surface water, hydration can occur, producing gypsum again. This hydration-dehydration cycle is a key factor in the interpretation of evaporite sequences and diagenetic histories. For broader context, see Evaporite deposits and the relationship to Gypsum within the calcium sulfate family.
Anhydrite minerals occur in a variety of settings beyond simple evaporites, including hydrothermal veins and certain sedimentary diagenetic environments. Because it forms and persists under different temperature and salinity regimes, anhydrite provides important clues about paleoenvironments and the evolution of basins. The mineral is also of interest in studies of isotopic composition and fluid history within sedimentary rocks, where comparisons to Isotope geology help reconstruct burial and alteration processes.
Economic and industrial relevance
The primary economic relevance of anhydrite lies in its role as a source of calcium sulfate for industrial applications. In the cement industry, calcium sulfate in the form of anhydrite can be used as a set-regulator to control the hydration of cementitious materials, complementing or substituting for gypsum (CaSO4·2H2O) in certain formulations. This helps manage the setting time and workability of Portland cement and related products. In some contexts, mined anhydrite is processed to supply sulfate and calcium for various industrial uses, or is used as a filler or additive in manufacturing. For chemical and agricultural purposes, the handling of calcium sulfate minerals, including anhydrite, is considered within broader Mining and chemical supply chains, with attention to impurities and processing requirements. See also Portland cement and Plaster for related materials that relate to calcium sulfate chemistry.
Environmental and safety considerations in the extraction and processing of anhydrite align with typical practices in mineral mining. Dust generation, handling of quarried rock, and the management of any associated brines or saline wastes are part of standard environmental planning in mining operations. See general discussions of Mining practices and environmental stewardship for mineral resources.
Debates and scientific context
Within geology and mineralogy, some debates concern the precise conditions and timing of anhydrite formation in complex basin histories. For example, researchers examine whether certain anhydrite-rich horizons formed primarily by direct precipitation from saline waters in evaporite basins, or by dehydration of gypsum during burial and diagenesis. Isotopic analyses and fluid inclusion studies are used to discriminate among these scenarios, contributing to broader discussions about paleoclimate, basin evolution, and the timing of mineral transformations in sedimentary sequences. These discussions are part of standard conversations in the study of sedimentary rocks, evaporites, and mineral paragenesis, and they are not unique to any political or ideological framing.