Calcite mineral forms rocks and has the chemical formula CaCO3. It is widespread and can be found in sedimentary, metamorphic, and igneous rocks all over the world. Some geologists consider it a "ubiquitous mineral," meaning it can be found anywhere.
Calcite is the most common form of calcium carbonate and is known for its varied and beautiful crystals. Calcite often occurs as scalenohedral and can be commonly twinned as heart-shaped or butterfly twins. The calcite crystals are generally found as rhombohedral terminations; however, there are shallow rhombohedral terminations, also known as nailhead spar.
Calcite is the main component of limestone and marble. These rocks are extremely common and account for a sizable portion of the Earth's crust. They are one of the world's largest carbon repositories.
Optical Spar is a highly transparent calcite. It is usually found as spectacular crystals, which are massive, either as marble or as limestone. The calcite can also be seen as earthy aggregates, fibres, nodules, and stalactites. The specimens of calcite specimens can occur in igneous rocks, hydrothermal veins, and metamorphic deposits.
Various Forms of Calcite
There are various forms of calcite that are found in multiple parts of the world.
Calcite as Oolitic Limestone: Oolitic limestone, a form of calcite is found in Tyrone, Pennsylvania, approximately ten centimetres in size.
Calcite as translucent onyx: Translucent Onyx, a form of calcite is found in Tecali, Mexico, approximately ten centimetres in size.
Double refraction in calcite: Iceland Spar, a form of transparent calcite, is found in Chihuahua, Mexico. This specimen exhibits excellent double refraction and is approximately ten centimetres in size.
Calcite as calcareous tufa: Calcareous Tufa, a form of calcite is found in Mumford, New York, approximately ten centimetres in size.
Calcite as travertine: Travertine is a form of calcite found in Tivoli, Italy, which is approximately ten centimetres in size.
Picasso Stone: Picasso Stone, a marbled variety with brown and black marks, is often cut and polished as cabochons to produce stones in jewellery and ornamental crafts.
White calcite as marble: Calcite in the form of white marble is found in Tate, Georgia, approximately ten centimetres in size.
Calcite Mineral- Natural Occurrence
Calcite is a common constituent of sedimentary rocks, mainly limestone, which is formed primarily from the shells of dead marine organisms. Limestone makes up about 10% of sedimentary rock. It is the main mineral found in metamorphic marble. It can also be found as a vein mineral in hot spring deposits, stalactites and stalagmites in caverns, volcanic or mantle-derived rocks such as carbonatites, kimberlites, and rarer cases, peridotites.
Calcite is a primary constituent of the shells of many marine organisms, including plankton (such as coccoliths and planktic foraminifera), the hard parts of red algae, some sponges, brachiopods, echinoderms, some serpulids, most bryozoa, and parts of some bivalves' shells (such as oysters and rudists).
Calcite can be found in spectacular form in New Mexico's Snowy River Cave, where microorganisms are credited with natural formations. Trilobites, which went extinct a quarter billion years ago, had compound eyes with lenses made of clear calcite crystals.
Calcite Formation Process
Calcite formation can occur via a variety of mechanisms, ranging from the classical terrace ledge kink model to the crystallisation of poorly ordered precursor phases (amorphous calcium carbonate, ACC) via an Ostwald ripening process or nanocrystal agglomeration.
Acc Crystallisation Can Take Place in Two Stages:
First, the ACC nanoparticles rapidly dehydrate and crystallise to form individual vaterite particles. Second, the vaterite undergoes a dissolution and reprecipitation mechanism, with the reaction rate controlled by the calcite surface area. The second stage of the reaction occurs at a rate that is approximately ten times slower. Calcite crystallisation, on the other hand, is pH-dependent and Mg-dependent in solution.
During mixing, a neutral starting pH promotes the direct transformation of ACC into calcite. When ACC forms in a solution with a basic initial pH, it transforms to calcite via metastable vaterite, which forms via a spherulitic growth mechanism. A surface-controlled dissolution and recrystallisation mechanism transforms vaterite to calcite in a second stage. Mg has a significant effect on the stability of ACC and its transformation to crystalline CaCO3, resulting in the formation of calcite directly from ACC.
What is Calcite Chemical Formula?
Calcite Formula: CaCO3
Calcite Chemical name: Calcium Carbonate
Calcite Mineral - Physical Properties
The major steps for Calcite production are as mentioned below:
Step 1: Crush the incoming minerals and transfer them to ball mills to convert them to powder form.
Step 2: Sieve the powder form and separate it into the desired grades.
Step 3: Split the powder in 3-micron, 5-micron, 10- micron bags as required.
The important fact is that with 100 tonnes of mine, 99.99 tons is extracted without any further additives.
Calcite crystal's properties make it one of the most widely used minerals. It is used as a building material, abrasive, agricultural soil treatment, construction aggregate, pigment, pharmaceutical, and other applications. It has more applications than nearly any other mineral.
Calcite as Limestone and Marble
Limestone is a sedimentary rock that is primarily composed of calcite. During diagenesis, it is formed by both the chemical precipitation of calcium carbonate and the transformation of shell, coral, faecal, and algal debris into calcite. Limestone is also formed as a deposit in caves as a result of calcium carbonate precipitation.
Marble is a metamorphic rock formed when limestone is heated and pressed. A close examination of a broken piece of marble will usually reveal visible calcite cleavage faces. The degree of metamorphism determines the size of the calcite crystals. Larger calcite crystals are found in marble that has been subjected to higher levels of metamorphism.
Calcite in Construction
The construction industry primarily consumes calcite in the form of limestone and marble. These rocks have been used as dimension stones and in mortar for thousands of years. Many of Egypt's and Latin America's pyramids were built with limestone blocks as the primary building material. Today, rough and polished limestone and marble are still popular materials in high-end architecture.
Calcite in limestone and marble are used in modern construction to make cement and concrete. These materials are easily mixed, transported, and placed as a slurry, which hardens into a durable construction material. Concrete is used to construct buildings, highways, bridges, walls, and a variety of other structures.
Calcite Mineral in Acid Neutralization
Calcite has a wide range of applications as an acid neutraliser. Limestones and marbles have been crushed and spread on fields as an acid-neutralising soil treatment for centuries. They are also heated to create lime, which has a much faster reaction rate in the soil.
In the chemical industry, calcite is used as an acid neutraliser. Crushed limestone is dispensed into streams to neutralise their waters in areas where acid mine drainage is a problem.
In medicine, calcium carbonate derived from high-purity limestones or marbles is used. Calcium carbonate is mixed with sugar and flavouring to make chewable tablets that are used to neutralise stomach acids. It is also found in a variety of medications used to treat digestive and other ailments.
Calcium Carbonate Sorbents
Sorbents are substances that can "capture" or "retain" another substance. Limestone is frequently treated and used as a sorbent material in the combustion of fossil fuels. Calcium carbonate reacts with sulphur dioxide and other gases released by combustion, absorbs them, and prevents them from escaping into the atmosphere.
Monuments and Statuary
Marble is a beautiful and easy-to-work-with stone that has long been used for monuments and sculptures. Its lack of significant porosity allows it to withstand freeze-thaw action outdoors, and its low hardness makes it a simple stone to work with. It has been used in projects ranging from the pyramids to a figurine. It is widely used in constructing cemetery markers, statues, mantles, benches, stairways, and other structures.
Many Other Uses
Calcite has a white colour when powdered. Calcite powder is frequently used as a white pigment or "whiting." Calcite was used in some of the first paints. It is a primary component of whitewash and is used as an inert colouring agent in paint.
Animal feed frequently contains pulverised limestone and marble as a dietary supplement. Cattle that produce milk and chickens that produce eggs require a calcium-rich diet. To increase calcium intake, small amounts of calcium carbonate are frequently added to their feeds.
Calcite Uses in Other Industries
The calcite is used as filler and coating material in most paper-producing industries to harden or smoothen, as necessary. Calcite allows rapid paper drying in the paper-making process due to its oil absorption feature. This makes it a useful ingredient in newspapers, magazines, and high-quality paper-making factories. Calcite is also used as a filling material for cigarette paper.
Calcite is used as a pigment material to prevent steel wear, increasing water and chemical resistance.
Calcite is the main material used as filler for rubber in tyre-producing factories. With calcite addition, the tyre is usable for a long time without loss of softness which lessens the elongation and stretching.
Calcite is also the primary filling material in plastic factories as it helps maintain the thickness everywhere. Also, it provides hardness and flexibility at the same time, along with being resistant to high temperatures.
To obtain larger agro-products from acid-bearing soil types, it is important to supply Ca in increased quantities. This is how life under Earth can be improved, and the pH must be between 6 and 7.5.
Calcite increases resistance to chemical effects in glass which is why it is used in glassmaking. It is also used in bottles and window glass making because it brightens the colour of the glass.
The finely ground limestone is used as a filler material in making glass glue due to its oil absorption properties.
Calcite is added to the tile slurry to remove the harmful effects of SiO2 in the medium. It also increases the strength of the ceramic material with its usage by 2-6%. If this percentage is increased, the percentage will change to pink or yellow speckles that will deform at high temperatures.
Calcite is used to maintain the hardness of the water and can control the watercolour or its cleaning.
Calcite Distribution Around the World
Calcite is found in almost every continent. There are large hued calcite deposits in Mexico and the USA. The calcite is distributed in the following places as per various nations.