Elements Help (page 2)
The elements include more than 100 known minerals. Many of the minerals in this class are made up of only a single element. Geologists sometimes subdivide this group into metal and nonmetal categories. Of all of the elements, 80% are metals. Gold, silver, and copper are examples of metals. Carbon produces the minerals diamond and graphite , which are nonmetals. Elements like phosphorus and selenium are also nonmetals.
For a complete listing of the known chemical elements, scientists use the Periodic Table of Elements . This is a chart that lists all the elements known today, along with a lot of other useful information. Besides the computer, the Periodic Table is probably the most important tool that scientists use.
Geologists use the Periodic Table to figure out the chemical composition of new minerals and to learn possible ways that different elements might bond.
The Periodic Table of Elements lists an element’s symbol (shorthand name, like C for carbon, Al for aluminum), atomic number (equal to the number of protons), atomic weight, and sometimes the atomic energy levels of the element. When a certain element is described, it is written with the atomic number in superscript and the atomic weight in subscript. On a Periodic Table, magnesium , with atomic number 12 and an atomic weight 24.31, is written as:
While the simplest of Periodic Tables show just an element’s atomic number and weight, complete charts give a broader amount of information. To give you an idea of the usefulness of the Periodic Table, the information listed for titanium in most Periodic Tables is shown below.
Knowing specifics about elements, like their electron arrangement, allows chemists and other scientists to figure out the bonding possibilities and types of compounds that can be formed with other elements. From this information, the mineral content of new and unknown samples is worked out. This information is also helpful when creating new compounds in the laboratory.
The halides are a group of nonmetals whose main chemical components include chlorine, fluorine, bromine, and iodine. Most halides are very soluble in water. They also form highly ordered molecular structures with a high degree of symmetry. Halite is the most common mineral of this group. It is known to most people as rock salt . Other halites include the minerals, cryolite , atacamite , fluorite , and diabolite .
A group of minerals, made up of one or more metals combined with oxygen, water, or hydroxyl (OH), is known as the oxides (and hydroxides ) group. The minerals in this group show a great variety of physical characteristics compared to other more nonchanging groups. Some oxides are hard and others soft. Some have a metallic luster, while some are clear and transparent. Some of the oxide minerals include anatase , corundum , chromite , and magnetite , while hydroxides include manganite , goethite , tungstite , and diaspore .
The s ilicates encompass the largest mineral group. As the name implies, these minerals have varying amounts of silicon and oxygen. Silicates are often opaque and light weight. Silicate minerals are different from other groups in that they are all formed as tetrahedrons . However, it can be tough to identify individual minerals within the silicates group. A tetrahedron is a chemical structure where a silicon atom is bonded to four oxygen atoms (SiO 4 ). Some representative silicates include albite , andesine , hornblende , microcline , labradorite , sodalite , leucite , and quartz .
The minerals of the sulfide group are often made up of a metal combined with sulfur. They are recognized by their metallic luster. The s ulfides are an economically important group of minerals. The extraction of sulfide ores from composite metals is a standard process in industry. Specific ores are known for certain metal extractions, like cinnabar (a major source of mercury), molybdenite (molybdenum, an alloy in steel), pyrite (iron source), and galena (lead, used in piping and pewter).
The sulfate mineral group usually combines one or more metals with the sulfate compound, SO 4 . Most sulfates are transparent to translucent, light in color, and soft. They usually have low densities. Gypsum , the most plentiful sulfate, is found in evaporite deposits. Common sulfates include anhydrite (CaSO 4 ) and c elestine (SrSO 4 ).
Sometimes, sulfates contain substituted groups like chromate , molybdate , or tungstate in place of the sulfate group. Chromates are compounds in which metals combine with chromate (CrO 4 ). The minerals crocoite (PbCrO 4 ), wulfenite (PbMoO 4 ), and scheelite (CaWO 4 ) are all examples of different group replacements that form different minerals. These compounds are usually dense, brittle, and brightly colored.
The mineral group, known as the phosphates , is made up of one or more metals chemically combined with the phosphate compound (PO 4 ). The phosphates are sometimes grouped together with the arsenate , vanadate , tungstate , and molybdate minerals. These minerals have substituted arsenic, tungsten, and molybdenum elements, respectively.
Although geologists list several hundred different types of these minerals, they are not common. Apatite is the most common phosphate mineral. Most minerals in these groups are soft, but their hardnesses can range from to 5 or 6 ( turquoise ). Although brittle, they have well-formed crystals in beautiful colors like lazulite (blue) and vanadinite (red or orange).
This is an easy one. Carbonates are minerals which contain one or more metals bonded with carbon in the compound (CO 4 ). Most pure carbonates are light colored and transparent. All carbonates are soft and brittle. They are usually found as well-formed rhombohedral crystals. Carbonates react with, bubble up, and dissolve easily in hydrochloric acid. Calcite is the most common carbonate. Other colorful carbonate minerals include rhodochrosite (pink to red), smithsonite (blue green), azurite (deep blue), and malachite (medium to dark green).
Nitrates and borates are often thought of as a subgroup of carbonates. They are formed when metal compounds combine with nitrogen and boron. When metals bond with nitrate, minerals like nitratine , a rare rhombohedral, transparent, often twinned mineral is formed.
When metals bond with borate, minerals like borax , kernite , and ulexite are formed. Most people have seen white borax, but it can also be colorless, gray, greenish, or bluish. Borax forms near hot springs, in ancient inland lakes, and places from which water has evaporated.
Minerals originally from organic sources (plants) are not usually classified as true (pure) minerals. However, some crystalline organic substances look and act like true minerals. These substances, formed primarily from carbon, are called organic minerals . Amber (petrified tree sap) is an example of an organic mineral.
Practice problems of this concept can be found at: Minerals and Gems Practice Problems
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