Fibers of Nonsilicate Minerals

From every chemical group mentioned in Dana s System of Mineralogy there are minerals that form as fibers. We began with the most commonly encountered minerals, the silicate and aluminosilicate groups, and now briefly mention a few from other chemical classes. 

Natural fibrous materials are identified somewhat by chance. For example, there are seven vanadate and seven vanadium oxysalt minerals on the list of fibrous minerals. These species are composed of a rare element, vanadium, but the fibrous samples may have attracted attention because they are often brightly colored. Vanadinite [Pb5(V04)3Cl] for example, is bright orange-red. Further, the list of natural mineral fibers we have compiled contains seventy-seven phosphate species. So many phosphates are listed because detailed descriptions of these mostly quite rare minerals were readily available (Nriagu and Moore, 1984). 

Only one phosphide mineral appears on the list. The tabulation contains twenty-six arsenate species but not a single arsenide. The fibrous minerals recorded reflect the limitations imposed by natural circumstances, and especially the opportunities for elements to be juxtaposed geochemically and able to produce a particular mineral compound. Oxygen containing compounds form by far the most prevalent natural fibers, but simple hydroxide and carbonate compounds are also prominent on the list. There are more oxyhalides and water-containing minerals than pure chloride minerals, al- 

The entire spectrum of inorganic fibers can be divided into two classes, based on differences in the crystallinity of the solids (Ray, 1978). Synthetic fibers have been known as man-made mineral fibers (MMMF) and manmade vitreous fibers (MMVF). But fibrous materials can be approached or divided in other ways. For example, in the Concise Encyclopedia of Chemical Technology (1985) the entry for chemical fibers includes both manmade and natural polymers, with the discussion centering on carbon-based compounds such as acetates, acrylics, and cellulose. Fibers of other inorganic compounds were not mentioned in the encyclopedia under this entry, but silica glass fibers were described under the heading Optical Fibers.  

A division based on crystallinity facilitates our discussions of both mineral and synthetic fibers by accentuating the morphology of the fibrous object rather than its source or composition. Further, although both amorphous and crystalline mineral fibers are known, most of these used in commerce—and certainly the best known—are crystalline. The opposite is true for synthetic or man-made inorganic fibers (MMIF). The fibers used in commerce are predominantly amorphous. 

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