- The Nature of Minerals
- The Formation of Crystals
- The External Form of Crystals
- Outward Appearance Of Crystalline Material
- Distorted and Deformed Crystals and Pseudomorphs
- Crystal Systems
Distorted CrystalsThese seldom approach perfection in their shapes but are more or less distorted, since their faces have not all enjoyed an exactly equal and perfect development. Probably faces develop unequally due to their relationship to the source of supply of the solutions carrying the atoms of which they are composed. Growing in confined spaces, as most crystals do, some faces, or sides, are likely to grow faster than others. Such crystals may appear to be drawn out, shortened or flattened, but the corresponding angles between faces are CONSTANT.
Deformed CrystalsThese have been bent and twisted out of their normal shape, usually by some later deforming force, so that the corresponding angles between faces may DIFFER WIDELY. This, however, is not a common occurrence.
Pseudomorphs(from PSEUDO, meaning FALSE, and MORPH I meaning FORM). After the original growth, if the chemical composition or the structure of a crystal becomes altered without modifying or destroying its original faces, the result is a crystal whose faces are unchanged but whose internal structure has become that of an entirely different mineral. The resulting crystal is known as a PSEUDO MORPH (pronounced SUE-doe-morf). Tiger's eye is an excellent example. In this mineral the original fibers, consisting of monoclinic crystals of crocidolite (pronounced kro-SID-oh-lite), or blue asbestos, have been replaced by minute grains of quartz that in mass, have retained the original external form of the crocidolite, but each of which has assumed the internal crystal structure for quartz.