The Inosilicates

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay

Inosilicates, from the Greek inos, fiber, are characterized by polymer chains of SiO4 tetrahedra. The chains link to strips of cation-oxygen octahedra.


The textbook pyroxene chain is shown above. In reality, the zigzag structures shown below are much more common.


Pyroxenoids have single chains, but because they either have too many or too few large cations, the chains are kinked differently from normal pyoxenes. As a result they lack the normal pyroxene cleavage.









Triple and Mixed Chains

Jimthompsonite (so named because the name thompsonite was already taken), Clinojimthompsonite and Chesterite aren't conspicuous minerals or very abundant. They are probably more abundant than we think simply because people don't look for them very often. But they are very important minerals because they was the first triple-chain silicates ever discovered. Chesterite, in addition, was the first mixed-chain silicate ever discovered, where double and triple chains alternate.

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Created 22 April 2013, Last Update