Applied to the structure of silicate minerals where SiO₄ tetrahedra are linked together into chains by sharing oxygens. Two important groups of rock-forming minerals are included: pyroxenes, where two of the four oxygens are shared to give a ‘single chain’ structure with the ratio Si:O = 1:3; and amphiboles, where half the SiO₄ tetrahedra share two oxygens and the other half share three oxygens, to give a ‘double chain’ or ‘band’ structure and a ratio Si:O = 4:11.