Chlorites
Chlorites are a group of hydrous aluminum silicates characterized by their soft green coloration and glassy luster. These minerals are composed of alternating layers of molecules that form two-dimensional sheets, with one layer containing silicate groups and aluminum atoms, and the other layer consisting of various metallic atoms such as magnesium and iron, bonded to hydroxyl groups. Notable members of the chlorite group include clinochlore, chamosite, nimite, and pennantite, each distinguished by their predominant metallic components.
Chlorites are primarily utilized in the form of clay minerals, which have applications in pottery, construction, and drilling operations. Their unique properties, including a relatively low hardness on the Mohs scale and chemical similarity to other clay minerals, make them valuable in various industrial processes. Chlorite's resistance to heat allows for its identification within clay samples through specific thermal testing and X-ray diffraction techniques. Typically found within metamorphic rocks like schists, chlorites often coexist with organic materials, quartz, and other minerals, contributing to their widespread presence in geological formations.
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Chlorites
Chlorites are most commonly found as microscopic particles in clays. They are also found in metamorphic rocks such as schists. Metamorphic chlorites are commonly found in Michigan, Norway, the United Kingdom, and Japan. Chlorites also occur in igneous rocks as a product of biopyriboles that have been transformed by heat and moisture. They may also be found in sedimentary rocks formed from pieces of older igneous or metamorphic rocks containing chlorites.
Definition
The term “chlorite” (from the Greek word for “green”) refers to a variety of hydrous aluminum silicates of magnesium, iron, and other metals. They are soft green minerals with a glassy luster. Chlorites are brittle and can be ground into white or pale green powder easily. Thin sheets of chlorite are flexible but not elastic.
Chlorites are a group of silicate minerals consisting of alternating layers of molecules forming two kinds of two-dimensional sheets. One layer consists of silicate groups (one silicon atom bonded to four oxygen atoms) bound to aluminum atoms, hydroxyl groups (one oxygen atom bonded to one hydrogen atom), and magnesium, iron, or other metallic atoms. The other layer consists of magnesium, iron, aluminum, or other metallic atoms bound to hydroxyl groups. If most of the metallic atoms other than aluminum are magnesium, the mineral is known as clinochlore. If the metallic atoms are iron, it is known as chamosite. If they are nickel, it is known as nimite. If they are manganese, it is known as pennantite. These four minerals are very similar.
Overview
Chlorites are most useful in the form of clay minerals. They mix with other substances to form clays that are widely used in pottery and construction. Clay minerals are also used in drilling “muds” (thick suspensions used to lubricate rotary drills). They may also be used as catalysts in petroleum refining and to decolorize vegetable oils.
The density of chlorite ranges from 2.6 to 3.3 grams per cubic centimeter. On the Mohs scale, they have a hardness between 2 and 2.5; they are generally soft enough to be scratched with a fingernail.
Chlorite usually exists as a microscopic component of clay, along with organic material, quartz, and other minerals. Visible pieces of chlorite may be found within a variety of rocks, particularly metamorphic rocks such as the very common schists.
Chlorites are chemically similar to other clay minerals (hydrous aluminum silicates) and are often found in combination with them. They are generally more resistant to heat than other clay minerals are. This fact is used to detect chlorite within clays. A sample of the clay is heated to between 500° and 700° Celsius, which breaks down the other clay minerals. X-ray diffraction is then used to detect the layers of silicate chains that are characteristic of clay minerals. If this pattern is detected, chlorite is present in the sample. In other regards chlorites have about the same properties as other clay minerals.