A novel process is reported that produces amorphous silica and nesquehonite (MgCO3·3H2O) from the magnesium silicate mineral olivine ((Mg, Fe)2·SiO4). The amorphous silica forms a supplementary cementitious material for use in concrete. The formation of nesquehonite sequesters carbon making the overall process carbon negative. Nesquehonite can also be used to form low-carbon construction products such as bricks, blocks and boards. This article reports on key process optimization studies. The potential for amorphous precipitated silica derived from olivine to produce carbon-negative concrete is discussed.