Approximately 2.5 kW-h/kg of energy are required to sufficiently activate granite powder so that it meets the ASTM requirement for mineral admixtures. Scanning electron microscopy/energy dispersive spectroscopy analysis shows evidence that a pozzolanic reaction occurs from the milled granite dust and an amorphous hydrated calcium silicate product is formed. X-ray diffraction, scanning electron microscopy/electron dispersive spectroscopy, particle size, surface area, and thermal characteristics (Thermogravimetric and differential scanning calorimetry) are described for milled and unmilled powders and mortar cube specimens. When used as a partial portland cement replacement in concrete, the compressive strength increases linearly with milling intensity.