Sodalite is a scarce mineral that can be rock forming. Sodalite is named in reference to its sodium content. It is used for carvings and some jewellery pieces. Its light to dark pure blue colour is well known in the semi-precious stone trade. Sodalite is a member of the feldspathoid group of minerals. Minerals whose chemistries are close to that of the alkali feldspars but are poor in silica (SiO2) content, are called feldspathoids. As a result or more correctly as a function of the fact, they are found in silica poor rocks containing other silica poor minerals and no quartz. If quartz were present when the melt was crystallizing, it would react with any feldspathoids and form a feldspar.. Localities that have feldspathoids are few but some produce large quantities of sodalite. Sodalite, when not blue, is hard to distinguish from other feldspathoids. It is the only feldspathoid that contains chlorine. Sodalite dissolved in a dilute solution of HNO3 gives a positive chlorine test obtained from some swimming pool test kits.