The revalorization of solid wastes and by‐products to be applied as solid particles in concentrated solar power (CSP) leads to cost savings and progresses toward more sustainable technology. Herein, the physicochemical, morphological, thermal, and solar absorption properties are evaluated for electric arc furnace dust, black slag from the steel industry, and Gossan waste from the Rio Tinto mining industry. The principal objectives of this work are (i) to carry out a thermal aging at 900 °C at different times, (ii) to assess the solid's stability throughout the evaluation of physicochemical, morphological, thermal, and optical properties of the material as received, after 300 and 500 h of thermal aging, and (iii) to determine the most appropriate candidate as a thermal energy storage medium and heat transfer fluid for the CSP concept with solid particles. The results show that electric arc furnace black slag is the most suitable candidate from the three solids studied, as it is the one that optimizes the combination of absorptance, thermal conductivity, and chemical stability after thermal aging.