Carbonate Mineral

All the crystalline structure of the carbonate minerals represents the trigonal symmetry of an ion, known as carbonate ion. This carbonate mineral is composed of a carbon atom. The carbonate mineral is centrally located in an equilateral triangle of the oxygen atoms. This anion group generally occurs in combination with calcium, uranium, sodium, iron, aluminium, manganese, zinc, copper, barium, lead, or other rare-earth elements. These carbonate minerals tend to be soft and is soluble in hydrochloric acid. This has a marked anisotropy in other physical properties which is the result of the planar structure of the carbonate ion.

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More about Carbonate Mineral

In about, there are 80 carbonate minerals, which are known to us, but most of them are rare to find. The most common varieties among others are – calcite, aragonite, dolomite. They are the prominent constituents of specific rocks – 

• Calcite is the principal mineral for the limestones and marbles

• Aragonite is found in the shells of organisms that have calcareous skeletons. 

• While, dolomite is a replacement for the calcite in the limestones, and when extensive, this rock is known as dolomite.

Yet other relatively similar carbonate minerals which serve as metal ores are – siderite for iron, strontianite for strontium, rhodochrosite for manganese, smithsonite for zinc, cerussite for lead, witherite for barium

Carbon Calcium 

Calcium carbonate is another chemical compound that has the formula as CaCO3. This is a common substance that is found in the rocks as the type of minerals like calcite and the aragonite (which is most notably known as the limestone which is a kind of sedimentary rock that majorly consists of calcite) which is the main component of the eggshells, snail shells, seashells and also the pearls.

The reaction formed is reversible. Calcium oxide will here react with carbon dioxide to form calcium carbonate. This reaction is quite driven to the right by emitting the carbon dioxide from the mixture. The production of calcium oxide from the limestone is the most common chemical transformations that are produced.

As similar to the metal carbonates, even calcium carbonate reacts with acidic solutions to produce carbon dioxide gas.

Aragonite

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Aragonite is another carbonate mineral. This is one of the three carbonate minerals which is the most common naturally occurring crystal form of the calcium carbonate mineral, chemical formula is CaCo3. Aragonite is formed by biological as well as by physical processes, including precipitation from the marine and freshwater.

The crystal lattice form of aragonite which differs from calcite, results in a different crystal shape, which is an orthorhombic crystal system with the acicular crystal. This has repeated twinning results in the pseudo-hexagonal forms. Aragonite may be columnar or in the form of fibrous, occasionally in branched helictites forms called the flowers of iron. 

Calcium Carbonate Chalk 

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Chalk is the soft, easy, fine-grained and pulverized, white-to-greyish textured variety of limestone. This chalk is composed of shells with minute and marine organisms like foraminifera, coccoliths, and rhodoliths. The pure variety form contains roughly up to 99 percent of the calcium carbonate in the form of mineral calcite.

Calcium Carbonate in Water 

Calcium carbonate is less soluble in pure water (15 mg/L at 25°C), but in the rainwater, this is saturated with carbon dioxide. In this case, solubility increases for the formation of even more soluble calcium bicarbonate. Calcium carbonate is quite unusual in that. The solubility increases with the temperature of the water being decreased.

Calcite and Aragonite 

Calcium Carbonate takes the form of two different minerals that are calcite and aragonite. Calcite is the stable form, while, aragonite is metastable. Over the time, or when this is heated, it can ultimately transform into the calcite form. Calcium carbonate generally crystallizes as calcite, but astonishingly at times, it forms aragonite in the seawater.

Calcium Carbonate Soluble in Water 

Calcium carbonate appears the same white, odourless powder and colourless crystals. They are practically insoluble in water.

Examples of Calcium Carbonate 

Calcite, aragonite and vaterite are examples of pure calcium carbonate minerals. Industrially they are an important source of rocks that are predominantly calcium carbonate which includes limestone, chalk, marble and travertine.
Calcium Carbonate Basic

The Carbonate salts are normally considered as weak bases, when they are applied on litmus paper, it turns the litmus paper blue.