The HMS bearing strata of the Mandiri deposit is ancient Kahayan alluvium, which was deposited during the Holocene age. In general, alluvium has varying thickness of between 2 m and 10 m. The lithology consists of loose quartz, medium grained intercalated grey mudstone containing carbonaceous, shale and bed load stream product; coarse grain sand layer.

Alluvium, Holocene age, pale black to dark brown peat (paludal deposit); loose sands, yellowish color, fine to coarse grained, unbedded (ancient Kahayan alluvium deposit); clay grey to brownish color, very soft, locally containing plant remains (tidal area); kaolinite clay. The thickness of this unit ranges from 50 to 100 m.

Werukin Formation (Tmw), middle Miocene to Pliestocene, this formation comprises brownish black conglomerate, compact, clast consists of quartzite and basalt fragments, diametere 1 – 3 cm, open fabric with matrix of sand. Alternating with yellowist sandstone, medium to coarse grained, locally exhibit crossbedding. intercallated grey mudstone, rather soft, carbonaceous, contain sub-bituminus coal seam partly, appear as interbedded within sandstone bed with the thickness of 20 – 60 cm. The Werukin Formation has 300 m in thickness. Werukin Formation is deposited in a paralic environment. Werukin Formation is the one of main coal bearing Formation in Barito Basin.

Geologically the HMS deposit at Mandiri is a placer deposit formed in a flood plain environment by concentration of ........

Mineral Sands can be extracted with two main techniques: open cut mining and suction dredging.

Open Cut Mining
Scrapers and bulldozers are used to dig higher quality resources including relatively hard minerals or layers, ensuring that the concentrate mined has a consistent combination. The scraper transports the material to a filtering facility, where it is crushed into 2mm granules. To eliminate tailings and extra clay particles, the filtered material goes through a complex series of spirals.

Suction Dredging
A dredge scoops mineral deposits from the bed of an artificial reservoir, that is built atop low-grade deposits to facilitate quick transportation of massive volumes of sand, and transports it to a separation facility via a suction pipe.

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