single-chain silicate minerals with Si-tetrahedral repeats of 3 (e.g., in wollastonite, CaSiO3), 5 (e.g., in rhodonite, MnSiO3), 7 (e.g., in pyroxmangite, FeSiO3), or 9 (e.g., in ferrosilite III). In contrast, the pyroxene tetrahedral repeat is 2. However, both the pyroxenoids and the pyroxenes have octahedrally coordinated cations connecting to the tetrahedral chains in similar ways. Hydrous pyroxenoids exist also, where Na + H substitute for one of the divalent cations, e.g., pectolite, Ca2NaH(SiO3)3. Wollastonite occurs as a contact metamorphic mineral of siliceous dolomites and is used in the manufacture of tile and in glazes. Rhodonite and pyroxmangite occur in manganese deposits and metamorphosed Mn-rich iron formations. Pectolite, commonly associated with zeolites, forms in cavities in basalts as a secondary mineral formed by hydrothermal activity.