Orthosilicate minerals as abrasives
Orthosilicate minerals, also known as nesosilicates, are a unique category of silicate minerals characterized by their distinct silicate groups, which are not interconnected. These minerals are primarily defined by the types of metal atoms attached to their silicate groups and are commonly found in igneous and metamorphic rocks worldwide. Due to their hardness, many orthosilicates are utilized as abrasives in various applications. The most prevalent orthosilicates include olivines and garnets, both of which are valued for their durability and aesthetic appeal.
Olivines, known for their green, glassy appearance, are sometimes used as gemstones called peridots, while garnets come in various colors and are frequently employed as both abrasives and ornamental stones. Other orthosilicates, such as andalusite, sillimanite, and kyanite, are specifically used in high-temperature environments, such as furnace linings, due to their thermal resistance. Additionally, minerals like topaz and zircon are recognized not only for their hardness but also for their beauty, making them popular choices for gemstone collectors. The diverse properties and applications of orthosilicates highlight their significance in both industrial and decorative contexts.
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Orthosilicate minerals as abrasives
Orthosilicates are silicate minerals (minerals containing silicon and oxygen) in which the silicate groups are not linked to one another. Found worldwide, they are often used as abrasives, and some are used as gemstones.
Definition
Orthosilicates, also known as nesosilicates, are distinguished from other silicates by the fact that their groups (one silicon atom bonded to four oxygen atoms) are not linked to one another. The properties of the different orthosilicates are determined by the type of metal atoms that are bound to the silicate groups. Orthosilicates are usually hard minerals with a glassy luster in a variety of colors. Orthosilicates are found worldwide, usually within and rocks. The most common orthosilicates are the olivines, which make up about 3 percent of the Earth’s crust by weight.
Overview
Because of their hardness, orthosilicates are often used as abrasives. Many orthosilicates are used as gemstones because of their varied colors and glassy luster. Some orthosilicates are used to line the interior of furnaces. A few orthosilicates are used as sources for certain elements.
Orthosilicates, unlike other silicates, have silicate groups that are not linked to neighboring silicate groups. These silicate groups may be bound to atoms of magnesium, iron, aluminum, oxygen, fluorine, manganese, calcium, chromium, zirconium, or titanium. They may also be bound to hydroxyl groups (one oxygen atom bonded to one hydrogen atom).
The most common orthosilicates are the olivines, which contain magnesium or iron. Olivines are green, glassy minerals. Transparent olivines, known as peridots, are used as gemstones. Garnets are a group of orthosilicates with various chemical compositions, usually containing aluminum atoms in combination with other metallic atoms. In some garnets another metal takes the place of aluminum. Garnets are hard, glassy minerals in a variety of colors including red, yellow, green, and brown. Garnets are often used as abrasives and gemstones.
Orthosilicates in which the silicate groups are bound only to aluminum atoms exist in three forms: andalusite (usually pink or red), sillimanite (usually white), and kyanite (usually light blue). All three varieties are often used to line the inside of furnaces because they resist high temperatures. Kyanite’s unusual color has led to its use as a gemstone.
Topaz is an orthosilicate containing aluminum and fluorine atoms along with hydroxyl groups. It is a very hard, glassy which is used as a gemstone. Topaz may be colorless, resembling diamond, or may be yellow, blue, brown, or green. Red topaz is rare. Yellow topaz turns pink when subjected to heat, and some colors of topaz fade when exposed to light.
Zircon, which contains zirconium, is a hard, brown, glassy mineral used as a gemstone or as a source of zirconium. Sphene, which contains calcium and titanium, is a moderately hard, brown, shiny mineral used as a source of titanium. Staurolite, which contains iron, aluminum, oxygen, and hydroxyl groups, is a hard, brown, glassy mineral which often occurs as intersecting crystals that form natural crosses used as decorations.
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