-
Many Industrial Uses of Kyanite
Kyanite is used to manufacture a wide range of products. An important use is in the manufacture of refractory products such as the bricks, mortars, and kiln furniture used in high-temperature furnaces. For foundries, the molds that are used for casting high-temperature metals are often made with kyanite. Kyanite is also in products used in…
-
Polymorphs of Al2SiO5
Three minerals have a chemical composition of Al2SiO5. These are kyanite, andalusite, and sillimanite. Kyanite is the high-pressure polymorph, sillimanite forms at high temperature, and andalusite is the low-pressure polymorph. Physical Properties of Kyanite Chemical Classification Silicate Color Blue, white, gray, green, colorless Streak White, colorless Luster Vitreous, pearly Diaphaneity Transparent to translucent Cleavage Perfect in…
-
Kyanite’s Unusual Hardness
Kyanite specimens have a variable hardness. The long crystals have a Mohs hardness of about 4.5 to 5 if tested parallel to the length of a crystal, and a hardness of 6.5 to 7 if tested across the short dimension of a crystal. The mineral was once commonly called “disthene” which means “two strengths.”
-
What is Kyanite?
Kyanite is a mineral found mainly in metamorphic rocks. It most often forms from the high-pressure alteration of clay minerals during the metamorphism of sedimentary rocks. It is found in the schists and gneisses of regionally metamorphosed areas and less often in quartzite or eclogite. Kyanite’s typical habit is a bladed crystal, although it sometimes occurs as radiating masses of crystals. Kyanite is often associated with…
-
Calcite: A Carbon Dioxide Repository
Carbon dioxide is an important gas in Earth’s environment. In the atmosphere it serves as a greenhouse gas that works to trap and hold heat near the surface of the planet. The process of limestone formation removes carbon dioxide from the atmosphere and stores it away for long periods of time. This process has been…
-
Many Other Uses
In a powdered form, calcite often has an extremely white color. Powdered calcite is often used as a white pigment or “whiting.” Some of the earliest paints were made with calcite. It is a primary ingredient in whitewash, and it is used as an inert coloring ingredient of paint. Pulverized limestone and marble are often…
-
Monuments and Statuary
Marble is an attractive and easily worked rock that has long been used for monuments and sculptures. Its lack of significant porosity allows it to stand up well to freeze-thaw action outdoors, and its low hardness makes it an easy stone to work. It has been used in projects as large as the pyramids and…
-
Uses in Acid Neutralization
Calcite has numerous uses as a neutralizer of acids. For hundreds of years, limestones and marbles have been crushed and spread on fields as an acid-neutralizing soil treatment. They are also heated to produce lime that has a much faster reaction rate in the soil. Calcite is used as an acid neutralizer in the chemical…
-
Uses of Calcite in Construction
The construction industry is the primary consumer of calcite in the form of limestone and marble. These rocks have been used as dimension stones and in mortar for thousands of years. Limestone blocks were the primary construction material used in many of the pyramids of Egypt and Latin America. Today, rough and polished limestone and…
-
Calcite as Limestone and Marble
Limestone is a sedimentary rock that is composed primarily of calcite. It forms from both the chemical precipitation of calcium carbonate and the transformation of shell, coral, fecal and algal debris into calcite during diagenesis. Limestone also forms as a deposit in caves from the precipitation of calcium carbonate. Marble is a metamorphic rock that…