Amorphous silica and silicates, and the carbonates and sulfates of calcium, strontium, and barium are the solids most commonly deposited by geothermal brines. The phenomenology and kinetics of their precipitation are reviewed in this paper. Practical methods of avoiding or reducing reinjection well damage are discussed, with emphasis on the important and well-researched problem of removing colloidal amorphous silica from spent geothermal brines before reinjection. Need for further research is also discussed. It is concluded that the interaction of the reinjected brine with the reservoir rock and the brine’s effect on rock properties are the areas that most need further research.