The mineralogical, geochemical, and statistical characteristics of recent fluvial deposits from the Brahmaputra–Jamuna River, Bangladesh, were examined to determine their provenance, transport dynamics, and depositional environment. Sediments were analyzed using X-ray diffraction (XRD), wavelength dispersive X-ray fluorescence (WD-XRF), field emission scanning electron microscopy (FE-SEM), and electron probe microanalysis (EPMA). Grain size analysis revealed a predominance of medium-to-fine sand (mean grain size 1.77–3.43 ϕ), with moderately well-sorted textures (sorting: 0.33–0.77 ϕ), mesokurtic to leptokurtic distributions, and skewness values ranging from −0.21 to +0.30. Mineralogical results show a high quartz content with minor feldspar, mica, zircon, rutile, and iron-bearing minerals. Geochemical data indicates high SiO₂ (63.39%–70.94%) and Al₂O₃ (12.25%–14.20%) concentrations and calculated chemical index of alteration (CIA) values ranging from 60.90 to 66.82. The microstructural study revealed angular to sub-angular grains with conchoidal fractures and stepped microcracks, indicating brittle deformation under high-energy conditions, which is consistent with short transport distances, limited sedimentary recycling, and a derivation from mechanically weathered source rocks. Multivariate analyses (PCA and K-means clustering) of grain size parameters reveal two distinct sedimentary regimes, namely Cluster 1 as finer-grained (2.36 ϕ), poorly sorted sediments, and Cluster 2 as coarser (2.98 ϕ), well-sorted deposits. Discriminant function values (Y₂: 78.82–119.12; Y₃: −6.01 to −2.56; V₁: 1.457–2.442; V₂: 1.409–2.323) highlight shallow water, fluvial/deltaic aspects, and turbidite depositional environments. These findings advance the understanding of sedimentary dynamics within large, braided river basins and support future investigations into the sustainable management of fluvial depositional environments.

Background: Mica is widely applied in cosmetics, construction, automotive, electronics, defense, and medical industries, particularly important in cosmetics as an ingredient in foundations, eyeshadows, lipsticks, and nail polishes for its pearlescent and shimmering effects. Aims: To evaluate the suitability of mica minerals from Bangladeshi river sands for cosmetic applications by investigating their chemical composition, heavy metal content, potential for skin irritation, and antimicrobial activity. Methods: The chemical composition, crystallographic structure, and heavy metal content of mica samples were analyzed using X‐ray fluorescence, X‐ray diffraction, and Atomic Absorption Spectroscopy. Non‐carcinogenic and carcinogenic risks were evaluated using USEPA models (ADD, HQ, HI, LADD, ILTCR). Sensory evaluation was performed by 10 trained panelists, while primary skin irritation was tested on albino rabbits. Antimicrobial activity against bacterial and fungal strains was assessed using agar well diffusion and broth microdilution assays. Results: Muscovite contained high Al ₂ O ₃ (30.46%) and SiO ₂ (49.29%), whereas biotite and phlogopite were enriched in Fe ₂ O ₃ (43%) and MgO, supporting shimmer, color, and UV‐protective properties. XRD confirmed high crystallinity and purity. Heavy metals were within safe dermal and inhalation exposure limits. Sensory evaluation showed a silky texture, strong adhesion, and a luminous finish. All samples were non‐irritant (PII = 0.00). Biotite and phlogopite exhibited moderate antibacterial activity against Staphylococcus aureus , Salmonella typhi , and Bacillus megaterium , but no antifungal effects. Conclusions: Muscovite, biotite, and phlogopite mica exhibit low heavy metal content, non‐irritant and non‐carcinogenic behavior, moderate antibacterial activity, and favorable sensory properties, highlighting their potential as safe, effective, and multifunctional ingredients for cosmetic applications.