Afwillite mineral occur as glassy, colorless to white prismatic monoclinic crystals. Afwillite is one of the calcium silicates that form when Portland cement sets to form concrete. The mineral is of practical importance because of its occurrence in cement. It occurs as an alteration mineral in contact metamorphism of limestone. Afwillite is typically found in veins of spurrite and belongs to the neosilicate sub-class. It forms at a temperature below 200 degrees C. It is composed of double chains that consist of calcium and silicon polyhedral connected to each other by sharing corners and edges. The crystal specimens of afwillite are available in the range of $50 to $100, varying mainly depending on their size.