The iron ore deposits are located within the southern part of the Krivorozhsky iron-ore basin. The iron mineralization is hosted by early Proterozoic rocks containing seven altered ferruginous quartzite strata with shale layers. The major iron ore bearing units in the open pit mines have carbonate-silicate-magnetite composition. In addition, oxidized quartzite is mined simultaneously with primary ore but cannot be processed at present and is stored separately for future possible processing. Only the magnetite mineralization is included in the 2015 open pit iron ore reserve estimates. The underground mine is hosted by a ferruginous quartzite with martite and jaspilite. The Kryvyi Rih Basin contains mostly Precambrian sedimentary-metamorphic rocks and is divided into three suites. The middle suite, with a thickness of up to 2,000 m, is the main ore-bearing formation. It consists of seven to eight seams of ferruginous quartzites (represented by hematites, magnetites, and mixed hematite-magnetite varieties) and schists. The average iron content is 30–40 percent in the ferruginous quartzites and 25–30 percent in the magnetite varieties (which compose 20 percent of the total quartzite reserves). Rich iron-ore bodies are dispersed throughout the ore-bearing formation. The ore is formed in columnar, lenticular, and pocket-like bodies that descend to a depth of over 1,000 m. In several places the bodies merge into large sloping ore beds. The rich ores are divided into magnetite, martite, and hematite-martite ores. The last two varieties have an average iron content of 63.7 percent and make up more than half of all reserves. The iron-formation succession at Kryvyi Rih/Krivoy Rog consists of seven members having a total thickness of ~1300 m (Alexandrov, 1973). It lies within the valley of the Ingulets River and its tributaries, the Saksagan and the Zheltaya, and extends in a NNE direction over an interval of about 100 km. The basin is developed within the crystalline basement of the Kurainian massif, comprising Archaean gneisses, granites, migmatites, amphibolites and schists exposed to the west and east of the 2200-2000 Ma Palaeoproterozoic Krivbass geosyncline. The Proterazoic Krivoi Rog Series within the Krivbass is divided into three sections: i). a lower arkose-quartzite and phyllitic sequence, with a horizon of talc schists; ii). a middle, ore-bearing ferruginous quartzite (banded iron formation - BIF) and slate sequence, which includes includes nine BIF horizons intercalated with quartz-sericite, chlorite-sericite, slates and microquartzites; and iii). an upper, quartzite-sandstone-slate sequence with lenses of marble. The Krivoi Rog Series is folded itno a complex synclinorial structure of synclinal and anticlinal folds with dips on the limbs of 45 to 80°, for the most part with a keel shaped synclinal closure plunging at up to 40° northwards. The limbs of the major synform has been intruded by Proterozoic granite and are cut by longitudinal faults or overthrusts, resulting in the ore-bearing units being segregated along the north-south strike of the basin to form the: i). southern-most Inguletsky, ii). the Saksagan or Main, iii). the Pervomaisk, iv). Annovsk, and v). the northern Zheltorechensk and Popel'nostovsk ore fields. The largest reserves of high grade ores are concentrated in the Saksagan ore field where the ore-bearing middle unit attains a thickness of up to 2000 m and contains up to eight BIF seams. The BIFs (locally termed 'ferruginous quartzites') comprise magnetite, magnetite-hematite, and hematite varieties, the most economically significant being the unoxidized magnetite and magnetite-hematite varieties. The high grade ores consist mainly of iron oxides and hydroxides which form column-like, less commonly stock-, and lens-like, and more rarely layer-like segregations and bodies within the BIF units, the characteristics of which vary from location to location within the basin. This high grade ore was formed by the leaching of quartz and oxidation of iron silicates within the BIFs.

The iron ore extracted from the Kryvyi Rih’s underground mine by a modified sub-level caving method.

Rich iron ores (with the useful component content 58 – 65% in the massif) of the Underground Mine Group (as underground mines) of the Mining Department of the PJSC “ArcelorMittal Kryvyi Rih” (the PJSC “ArcelorMittal Kryvyi Rih”) are mined applying underground methods at the depths of over 1100 m. Deepening of mining operations causes deterioration of mining-geological conditions of the iron ore deposit. Decrease of the deposit thickness and iron content in ores is one of the major deterioration indicators. Iron content decrease results in loss of iron ore consumers as current leading iron ore producers offer ores with iron content of not less than 62%.

The minefield of the deposit is located in the southern part of Saksahanska band which is the eastern Kryvorizka syncline limb. The deposit contains six schist and six ferruginous levels.

The fifth horizon is an economic one and occurs directly on the rocks of the 5th schist level excluding the anticlinal part where the 5th ferruginous level rests on the 4th ferruginous and schist level rocks due to several complicated tectonic shifts.

This level is the richest in ore and its thickness is 45 – 120 m. The lithographic composition of the level is characterized by dominance of martite hornfels and jaspilites over hydrohematite-martite hornfels and jaspilites occurring in the form of small benches in the hanging and footwalls of the thickness and above iron-mica-martite hornfels and jaspilites.

The largest deposits of martite and hydrohematite-martite ores are assigned to the 5th ferruginous level.

At present, level 1045 m is the main production one of the Underground Mine Group of the PJSC “ArcelorMittal Kryvyi Rih”, level 1135 m is in the process of building.

The ore body at the main levels is opened by haulage crosscuts. Preparation of a haulage level is fulfilled by the ort-ring pattern where field haulage drifts in the footwall and access crosscuts from the western drift are driven.

An interval between levels is 90 m and a level consists of three sublevels. Deposit opening at intermediate levels is performed by crosscuts from auxiliary sub-verticals of shafts to fringedrifts and then by orts driven from these drifts.

At the Underground Mine Group, level block preparation of the ore body is applied. For this, the ore body within the level is divided on strike into 100 m long blocks as wide as the horizontal thickness of the ore body. The block is divided vertically into three sublevels of 30 m in height each. A sublevel consists of extraction panels mined onto two scraping orts with the following transportation of the ore along the storage drift to the orepass raise where the ore is passed to the main haulage level for loading into electromotive cars.

Due to low hardness of ore and country rock, a relatively low value of mined iron ores at the Underground Mine Group, the sublevel caving system is only used for mining. In addition, the system of drilling the ore massif with a bunch of deep raising holes from drilling cutouts of the level onto the vertical slot (compensation area) has been applied for a long time.

The iron ore is crushed and screened at surface into lump and sinter ore, before being transported by rail to the steel plant.