<p>Basalt is a critical raw material for continuous fiber production; however, its inherent heterogeneity causes unstable fiber performance, hindering its industrial application. Moving beyond the sole use of chemical composition for ore selection, this study decoupled the effects of macroscale structure and microscale texture from mineralogical influences. We systematically investigated three basalts with highly similar chemical and mineralogical compositions but distinct petrographic features: B1 (aphanitic and non-vesicular), B2 (phaneritic and non-vesicular), and B3 (phaneritic and vesicular). Combined analyses (differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy, fiber drawing, and tensile testing) revealed that the structure/texture dictated the intermediate-temperature (1050–1180&#xa0;°C) melting pathway by modulating kinetics and intermediate phase formation (e.g., Fe-rich spinel). The melting history predetermined the final melt microstructure: rapid melting (B1) created a highly disordered network with a low glass transition temperature (<i>T</i>_g) but relatively higher crystallization resistance (large Δ<i>T</i>), whereas slower melting (B2/B3) yielded more ordered melts with higher <i>T</i>_g and lower Δ<i>T</i>. This difference directly affects the fiber quality. Although all fibers showed comparable average tensile strengths, those derived from the B2 melt exhibited the lowest variability under the laboratory conditions (coefficient of variation = 12.7%; 95% CI [9.3%, 17.7%]), along with the most uniform diameter. This study established that, for basalts of equivalent chemistry, the original rock texture and structure may be key factors for ore quality, providing a novel petrological criterion to guide resource selection for fiber production where low variability in performance is desired.</p>