Portlandite is a mineral that is primarily composed of calcium and hydroxide. The name comes from the location where it was first discovered, Portland, England. Portlandite is also known as calcium hydroxide, hydrated lime, or slaked lime. Other synonyms for portlandite include milk of lime, lime water, and pickling lime. Portlandite is a common ingredient in many industrial and construction processes, including the production of cement, water treatment, and soil stabilization. It is also used in agriculture as a source of calcium for plants. Despite the various synonyms for portlandite, the mineral remains an important component in many industrial and scientific applications.