Pyrite ${\mathrm{FeS}}_2$ is an approximately 1-eV-band-gap semiconductor composed of exceptionally earth-abundant, low-cost, and nontoxic elements, with applications in numerous electronic and energy technologies. Facile and scalable synthesis of ${\mathrm{FeS}}_2$ from natural resources is thus highly desirable but must generate high-purity, semiconductor-quality material to access the widest range of applications. Here, we demonstrate that various forms of commercial iron ore, most notably taconite-based ore, can be used to synthesize semiconductor-quality ${\mathrm{FeS}}_2$ via remarkably simple methods, despite very high initial impurity content. These ores can be reduced to Fe, sulfidized to ${\mathrm{FeS}}_2$, then used in vapor-phase crystal growth to synthesize surprisingly high-quality ${\mathrm{FeS}}_2$ with no additional purification. This is found to be possible due to two synergistic effects: very few elements efficiently dope ${\mathrm{FeS}}_2$, and the sulfidation and crystal growth steps introduce significant unexpected purification, which we track via detailed trace element analyses and rationalize via thermodynamic parameters. The result is pyrite single crystals with room-temperature Hall electron densities down to a remarkable ${10}^{16}{\mathrm{cm}}^{-3}$ with corresponding mobilities exceeding $100{\mathrm{cm}}^2{\mathrm{V}}^{-1}{\text{s}}^{-1}$, surprisingly close to crystals grown from high-purity reagents. We thus demonstrate facile synthesis of semiconductor-quality ${\mathrm{FeS}}_2$ from commercial iron ores, potentially unlocking a new renewable-energy revenue stream for an abundant natural resource.

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• Batteries
• Electrocatalysis
• Photocatalysis
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• Sample preparation