Mg
Fe
Si
O
H

Jimthompsonite

Jimthompsonite is an inosilicate with a triple chain silicate backbone. Pyroxenes have a single chain, amphiboles have a double chain, and jimthompsonite and a few other minerals have even wider chains.

Veblen, D.R., and C.W. Burnham. 1978. New biopyriboles from Chester, Vermont: II. The crystal chemistry of jimthompsonite, clinojimthompsonite, and chesterite, and the amphibole-mica reaction. American Mineralogist 63:1053-1073