Sedimentide

Sedimentide is a hypothetical mineral discussed in speculative geoscience literature as a diagenetic cement that forms in sedimentary basins. It is described as a mixed-phase material, combining silica-rich nanocrystalline components with aluminosilicate and carbonate elements, resulting in a microcrystalline to fine-grained matrix that binds sediment grains. Because it is a theoretical construct rather than a single fixed composition, its exact makeup varies between descriptions.

Formation and occurrence: Sedimentide is said to form during burial and diagenesis when pore waters become supersaturated with silica, alumina, and carbonate species. Precipitation of these components can fill pore spaces and cement grains in sandstone, siltstone, and certain carbonate rocks. It may also occur as nodules or concretions within sedimentary sequences.

Structure and properties: The phase is depicted as a microcrystalline to amorphous matrix that intergrowths with minerals such as quartz, calcite, dolomite, and clays (for example illite or kaolinite). Because it is described as a mixture rather than a discrete mineral, properties vary in speculative accounts. Reported characteristics include a hardness in the mid-Mohs range, variable coloration from gray to brown, and a dull to glassy luster. Solubility is described as relatively low in pure water, with carbonate-rich examples dissolving under acidic conditions.

Significance: In teaching and theoretical discussions, sedimentide serves as a model for understanding diagenetic cementation and pore-fluid interactions in sedimentary rocks. Some sources treat it as a provisional name awaiting formal mineralogical definition rather than an established mineral species.

Etymology: The name combines sedimentum, meaning deposit, with the mineral suffix -ide. Related topics include diagenesis, cementation in sedimentary rocks, and diagenetic minerals.