compound with a structure in which silicate tetrahedrons (a central silicon atom surrounded by four oxygen atoms at the corners of a tetrahedron) are arranged in rings. Each tetrahedron shares two of its oxygen atoms with other tetrahedrons; the rings formed may have three (e.g., benitoite), four (e.g., axinite), or six members (e.g., beryl). The cyclosilicates have chemical formulas that contain multiples of SiO₃.