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This research aims to concentrate and recover valuable heavy minerals (VHMs) contained in Diit area, southern coast of the Red Sea, Egypt. In this study, three technological samples were collected representing Lens, Delta and Wadi Diit; mineralogical investigation followed by mineral processing was performed in order to recover VHM content. VHMs such as zircon, ilmenite, rutile, sphene, apatite, garnet, and magnetite have been recorded in associations with lesser amounts of uranothorite, monazite, xenotime, fergusonite, khatyrkite, and gold. Initially, two stage wet gravity concentration processes, rougher and scavenger, were carried out via a shaking table to produce a clean concentrate of VHMs, which was used as feed material for the magnetic separation process. Magnetic separation was performed in order to separate ferromagnetic minerals from paramagnetic minerals as well as diamagnetic minerals to obtain clean concentration of these fractions. Assay and Material balance of the concentration steps proved that the THM content of Diit lens increased to 89.70% with a recovery of 91.68% in a weight of 61.08% out of the original sample. While the percentage of THM content in Wadi and Delta Diit samples increased to 48.68 and 47.67% respectively, with recovery equivalent to 71.67 and 82.06% respectively in a weight of 16.51, 18.7% respectively out of the original sample. Finally, a process flowsheet was created according to the optimum conditions for concentration and separation processes.

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This paper tries to elucidate the origin of the siliceous rocks (cherts) within the Turonian flint‐bearing chalky limestone member of Abu Roash Formation, Abu Roash area, north Western Desert, Egypt. Understanding the formation mechanism of the studied chert was gained through field and petrographic investigations, supplemented by geochemical analyses of both cherts and host Turonian carbonates. The field observations reveal that the chert is found in two forms: banded and nodular. The microscopic investigation determined that the cherts exhibit two types of silica: replacive silica (cryptocrystalline and microcrystalline quartz) and silica cement (length‐fast chalcedony and megaquartz). The chert texture corroborates that the examined authigenic silica was formed diagenetically by the replacement and void‐filling of the host carbonate rocks. The silica was most likely derived from the biogenic opal‐A of the siliceous radiolarian tests. The silica‐phase transformation started with the dissolution of the biogenic opal‐A and precipitation of opal‐CT. Subsequently, opal‐CT was recrystallized into crypto‐ and microquartz at low pH and high temperature. The length‐fast chalcedony and megaquartz occur later as infill to the cavities and pore spaces. The formation of chert is interpreted to be a result of mixing marine–meteoric waters. The effect of the freshwater diagenesis on carbonates is manifested by the dissolution of the allochems, precipitation of granular, drusy, and blocky calcite (meteoric cements), aggrading neomorphism of matrix, and calcitization of the skeletal particles. Geochemical analyses of the host carbonates indicate nearly flat REE patterns and absence of a negative Ce anomaly. This confirms the deviation from the typical seawater and supports the effect of phreatic meteoric water in the chert formation. The paragenetic relationships reveal that the chertification process was performed after dolomitization and before the carbonate meteoric cementation.

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