Colemanite mineral (C-3 mm) and milled colemanite minerals (C-75 µm and C-45 µm powders) were obtained from Eti Maden Bigadic Boron Operation Directorate. The C-3 mm initial material was milled in a high-energy ball mill. This material was then sifted using a sieve with a size of 25 μm according to the ASTM standard (C-25 μm) for the purpose of producing submicron-sized/nano-sized particles. Thermal properties of the C-3 mm mineral, C-75 µm powder, C-45 µm powder and C-25 μm powder were examined using ThermoGravimetry (TG)/Differential Thermal Analysis (DTA) device. In DTA measurement, first decomposition temperature appeared with a high intensity endothermic peak at 406°C for the C-3 mm mineral and existed with an endothermic peak at 388°C for the C-25 μm powder. In Differential TG measurement, the first decomposition temperature seemed with a high intensity-narrow endothermic peak at 403°C for the C-3 mm mineral and occurred with an endothermic peak at 388°C for the C-25 μm powder. In a previous study, the C-75 μm, C45 μm and C-25 μm powders have been added to Portland cement concrete at varying ratios. Based on the results obtained, it was noted that the compressive strength of concrete increases significantly. Such findings are thought to shed light on engineering research related to nano-sized boron minerals.