What Is The Physical Makeup Of A Rock
A rock can be defined as a solid substance that occurs naturally because of the effects of three basic geological processes: magma solidification; sedimentation of weathered rock debris; and metamorphism. As a result of these processes, three main types of rock occur:
Sedimentary Rocks - formed by burial, compression, and chemical modification of deposited weathered rock droppings or sediments at the Earth's surface.
Metamorphic Rocks - created when existing rock is chemically or physically modified past intense heat or pressure.
Most rocks are equanimous of minerals. Minerals are defined past geologists equally naturally occurring inorganic solids that have a crystalline structure and a distinct chemic limerick. Of course, the minerals found in the Earth's rocks are produced by a variety of different arrangements of chemical elements. A listing of the eight most common elements making upwardly the minerals found in the Globe's rocks is described in Table 10d-1.
Tabular array 10d-1: Common elements found in the Earth's rocks.
| Element | Chemic Symbol | Percent Weight in Earth's Crust |
| Oxygen | O | 46.sixty |
| Silicon | Si | 27.72 |
| Aluminum | Al | 8.xiii |
| Iron | Atomic number 26 | 5.00 |
| Calcium | Ca | 3.63 |
| Sodium | Na | two.83 |
| Potassium | Chiliad | 2.59 |
| Magnesium | Mg | two.09 |
Over 2000 minerals have been identified by globe scientists. Tabular array 10d-2 describes some of the important minerals, their chemical limerick, and classifies them in one of nine groups. The Elements Group includes over ane hundred known minerals. Many of the minerals in this class are composed of only i element. Geologists sometimes subdivide this grouping into metal and nonmetal categories. Gold , silver , and copper are examples of metals. The elements sulfur and carbon produce the minerals sulfur , diamonds , and graphite which are nonmetallic.
Figure 10d-i: Silver.
Figure 10d-2: Copper.
Figure 10d-3: Graphite.
The Sulfide Group are an economically important class of minerals. Many of these minerals consist of metallic elements in chemical combination with the chemical element sulfur. Most ores of important metals such equally mercury ( cinnabar - HgS), iron ( pyrite - FeSii ), and atomic number 82 ( galena - PbS) are extracted from sulfides. Many of the sulfide minerals are recognized by their metallic luster.
Figure 10d-4: Pyrite.
Figure 10d-five: Galena.
The Halides are a grouping of minerals whose principle chemical constituents are fluorine, chlorine, iodine, and bromine. Many of them are very soluble in water. Halides as well tend to have a highly ordered molecular structure and a high degree of symmetry. The nigh well-known mineral of this group is halite (NaCl) or rock common salt.
Figure 10d-six: Halite or rock table salt.
The Oxides are a group of minerals that are compounds of i or more metallic elements combined with oxygen, h2o, or hydroxyl (OH). The minerals in this mineral group show the greatest variations of physical properties. Some are difficult, others soft. Some have a metallic luster, some are clear and transparent. Some representative oxide minerals include corundum , cuprite , and hematite .
Figure 10d-7: Corundum
Figure 10d-viii: Hematite
The Carbonates Group consists of minerals which comprise one or more metallic elements chemically associated with the chemical compound CO3 . Virtually carbonates are lightly colored and transparent when relatively pure. All carbonates are soft and brittle. Carbonates as well effervesce when exposed to warm hydrochloric acid. Most geologists considered the Nitrates and Borates as subcategories of the carbonates. Some mutual carbonate minerals include calcite , dolomite , and malachite .
Effigy 10d-ix: Calcite.
Figure 10d-x: Dolomite.
The Sulfates are a mineral group that incorporate 1 or more metallic element in combination with the sulfate chemical compound SO4 . All sulfates are transparent to translucent and soft. Near are heavy and some are soluble in h2o. Rarer sulfates exist containing substitutions for the sulfate compound. For case, in the chromates SO4 is replaced by the chemical compound CrO4 . Ii common sulfates are anhydrite and gypsum .
Figure 10d-11: Gypsum.
The Phosphates are a group of minerals of i or more than metallic elements chemically associated with the phosphate compound POiv . The phosphates are often classified together with the arsenate, vanadate, tungstate, and molybdate minerals. One common phosphate mineral is apatite . Most phosphates are heavy but soft. They are normally breakable and occur in small crystals or compact aggregates.
The Silicates are by far the largest group of minerals. Chemically, these minerals contain varying amounts of silicon and oxygen. It is easy to distinguish silicate minerals from other groups, just hard to identify individual minerals within this grouping. None are completely opaque. Most are calorie-free in weight. The construction component of all silicates is the tetrahedron. A tetrahedon is a chemical structure where a silicon atom is joined by four oxygen atoms (SiOiv). Some representative minerals include albite , augite , beryl , biotite , hornblende , microcline , muscovite , olivine , othoclase , and quartz .
Figure 10d-12: Albite.
Figure 10d-12: Biotite.
Figure 10d-xiii: Hornblende.
Figure 10d-fourteen: Olivine.
Figure 10d-15: Orthoclase.
Effigy 10d-sixteen: Quartz.
The Organic minerals are a rare grouping of minerals chemically containing hydrocarbons. Most geologists do not allocate these substances as truthful minerals. Note that our original definition of a mineral excludes organic substances. However, some organic substances that are found naturally on the Earth that exist as crystals that resemble and act like true minerals. These substances are called organic minerals. Amber is a good example of an organic mineral.
Source: http://www.physicalgeography.net/fundamentals/10d.html
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