<p>Rock powders are increasingly considered a sustainable alternative to soluble fertilizers, particularly in highly weathered tropical soils. In this context, this study aimed to evaluate the short-term chemical and mineralogical changes induced by a diabase–shale–dolostone blend applied as a soil remineralizer to a Ferralsol under controlled laboratory conditions. Specifically, the experiment assessed nutrient release, changes in soil chemical attributes, and dissolution–precipitation features on mineral surfaces. A 1-year pot experiment was conducted in Rio Claro (SP, Brazil), using four remineralizer treatments and a control, each with three replicates. The treatments combined two application rates (15 and 20 t ha⁻¹) with two particle-size fractions: filler (&lt; 0.3&#xa0;mm) and powder (0.3–2.0&#xa0;mm). Additionally, individual fragments of diabase and dolostone (2–5&#xa0;mm) were enclosed in mesh bags to monitor surface weathering. Soil and fragments were sampled twice a year, while leached water was collected monthly. The remineralizer's application positively affected the soil, raising pH, base saturation, and the available levels of SO₄²⁻, Ca²⁺, and Mg²⁺, as well as reducing Al³⁺ and Al saturation. New phases of clay minerals such as chlorite, vermiculite, and hydroxy-interlayered minerals (HIMs) were observed. The leachate evaluations showed the availability of K⁺, Ca²⁺, Mg²⁺, and Na⁺, along with the soil's permanence of Al³⁺, Si, and P. In fragments, the rapid precipitation of poor crystalline material—kaolinite-like phase (KLP)—demonstrates that rock powder reduced exchangeable acidity. The rock powder blend holds potential as a nutrient source for soil, especially secondary macronutrients, warranting future agronomic testing.</p>