The aim of this research is to investigate the phase composition and structural peculiarities of complex metamorphic manganese ores from Central Kazakhstan before and after sintering in the temperature range of 600–1200 °C in an air atmosphere. X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and optical microscopy were used to analyze changes in elemental and phase composition. In their initial state, according to XRF analysis, the Bogach ore was manganese-rich, with a manganese content of 60.77 wt.%, while the Zhaksy ore contained manganese (44.88 wt.%), silicon (20.85 wt.%), and iron (6.14 wt.%) as its main components. In the Bogach ore samples, manganese content increased from 60.77% to 65.7% as the sintering temperature rose to 1100 °C, while the hausmannite phase (Mn₃O₄) emerged as the dominant phase, comprising 95.77% of the crystalline component at 1200 °C. Conversely, the Zhaksy ore samples displayed a sharp increase in braunite-phase (Mn₇O₁₂Si) content, reaching 83.81% at 1100 °C, alongside significant quartz amorphization. The degree of crystallinity in Bogach ore peaked at 56.2% at 900 °C but declined at higher temperatures due to amorphous phase formation. A surface morphology analysis revealed the transformation of dense, non-uniform particles into porous, granular structures with pronounced recrystallization as the temperature increased. In the Bogach samples, sintering at 900 °C resulted in elongated, needle-like crystalline formations, while at 1200 °C, tetragonal crystals of hausmannite dominated, indicating significant grain growth and recrystallization. For Zhaksy samples, sintering at 1100 °C led to a porous morphology with interconnected grains and microvoids, reflecting enhanced braunite crystallization and quartz amorphization. These findings provide quantitative insights into optimizing manganese oxide phases for industrial applications, such as catalysts and pigments, and emphasize the impact of thermal treatment on phase stability and structural properties. This research contributes to the development of efficient processing technologies for medium-grade manganese ores, aligning with Kazakhstan’s strategic goals in sustainable resource utilization.

The replacement of clay by coal ash in fired brick is limited by the resulting strength loss. This study examines whether a calcined manganese ore can color a brick body containing ash-slag waste (ASW) without reducing its strength. Four mixes of a medium-plasticity clay with 0 or 20 wt.% ASW (Pavlodar thermal power plant TPP-1) and 0 or 7 wt.% Bogach manganese ore calcined at 1200 °C were fired at 950 °C and characterized by X-ray fluorescence, X-ray diffraction with Rietveld refinement, image-based CIELAB colorimetry and physico-mechanical tests. In the ASW-containing body, the ore raised the mean compressive strength from 9.89 ± 1.33 to 12.41 ± 3.46 MPa (three specimens per mix, p = 0.34) without significant changes in water absorption and density; by mean strength, this body corresponds to grade M100 (GOST 530-2012), class f_b ≥ 10 MPa (EN 771-1) and grade NW (ASTM C62-17). Hausmannite (Mn₃O₄) introduced with the ore persisted as a crystalline phase after firing in both ore-containing mixes (about 2% of the crystalline fraction); the mechanism of the strength change was not established. The ore lowered the lightness L* of the ASW-containing body from 67.3 to 43.3 (ΔE₀₀ = 22.9) at an essentially constant hue angle (57–60°); the fired body is dark brown.