http://mineralogy.frequentlyasked.info Just another WordPress weblog Mon, 24 Sep 2007 18:12:12 +0000 http://backend.userland.com/rss092 en Ionic crystals’ structures are all based on a fundamental group of atoms (or, more accurately, ions) consisting of one silicon atom surrounded by four oxygens - the Si04-group, which is the "unit brick" of silicate structure. The oxygens are arranged at the four corners of a regular tetrahedron, with ... http://mineralogy.frequentlyasked.info/2007/09/24/ionic-crystals/ Previously, crystals were defined as bodies bounded by usually flat surfaces, arranged in a regular manner expressing the internal arrangement of the atoms. The study of the arrangement of atoms within a crystal, that is, of atomic structure, has been made possible in recent years by new methods of ... http://mineralogy.frequentlyasked.info/2007/09/21/atomic-structure-of-minerals/ There are certain conventions with regard to the lettering and order of the crystallographic axes. In the most general case, that in which the unit form cuts all three axes at unequal lengths and in which none of the axes is at right angles to any other, the crystallographic ... http://mineralogy.frequentlyasked.info/2007/09/20/lettering-and-order-of-the-crystallographic-axes/ Crystallographic symmetry must not be confused with geometrical symmetry. Crystallographic symmetry depends upon the internal atomic structure of the crystal, and as the arrangement of the atoms is the same for parallel planes, it follows that the angular position is the only factor concerned, and that the sizes of ... http://mineralogy.frequentlyasked.info/2007/09/19/crystallographic-and-geometrical-symmetry-2/ It has already been mentioned that crystals are built up of an orderly arrangement of the atoms or atomic groups of the mineral. Examination of crystals by X-rays has led to the determination of the relative positions of the different atoms in the structure. If the atoms are represented ... http://mineralogy.frequentlyasked.info/2007/09/18/law-of-the-constancy-of-interfacial-angles/ In was noticed by the ancient Greeks that a certain mineral, quartz, usually occurred in forms having a characteristic shape, being bounded by flat faces. From the transparency of this mineral and the occurrence in it of included material, it was thought that quartz resulted from the freezing of ... http://mineralogy.frequentlyasked.info/2007/09/17/elements-of-crystallography/ The specific gravity of a body is the ratio of the weight of the body to that of an equal volume of water. This latter weight varies with the temperature, and this variation has to be considered in exact work. In the general practice of determinative mineralogy, however, this correction ... http://mineralogy.frequentlyasked.info/2007/09/14/specific-gravity/ Hardness Standard Mineral 1 Talc 2 Rock-salt, or Gypsum 3 Calcite 4 Fluor-spar 5 Apatite 6 Orthoclase Felspar 7 Quartz 8 Topaz 9 Corundum 10 Diamond Window-glass may be used in an emergency as a substitute for apatite, and flint for quartz. The hardness test may also be made by endeavoring to scratch the specimens enumerated 'in the list with the mineral under examination. If, for example, the mineral scratches orthoclase felspar but ... http://mineralogy.frequentlyasked.info/2007/09/13/mohs-scale-of-hardness/ Gases and liquids Oxygen, nitrogen and carbon dioxide are examples of natural gases; and water, mercury and petroleum are examples of natural liquids. Solids With the exception of mercury and the natural mineral oils, all the minerals with which we have to deal are found in the solid state, and the ... http://mineralogy.frequentlyasked.info/2007/09/13/state-of-aggregation/ Minerals possess certain physical properties that are considered in this chapter in the following order: Certain characters depending upon light, such as color, luster, transparency, translucency, phosphorescence and fluorescence. Other optical properties especially valuable in the recognition of minerals in thin section under the microscope are dealt with in a ... http://mineralogy.frequentlyasked.info/2007/09/12/physical-properties-of-minerals/