Calcite’s crystal 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.

It is one of the most difficult of all minerals to be cut because of perfect cleavage in 3 directions. The cost of faceted stone is therefore mostly in the labor of cutting.

It can be scratched readily by a knife blade or geologic pick. It has a specific gravity of 2.71. Three perfect cleavages give calcite its six-sided polyhedrons with diamond-shaped faces; the angles defining the faces are 78° and 102°.

The atoms inside a fluorescent mineral like calcite are orbited by electrons. This orbit is regular and steady until it’s struck by UV light. This ray of light puts the electrons in a spin.

It is typically colorless or white, however impurities can color calcite shades of red, yellow, orange, green, blue, purple, brown and black, and it can be multicolored or banded.

How can you tell the difference between a piece of quartz and calcite?

Quartz crystals typically have a well defined hexagonal (6-sided) shape, with prismatic crystals that are striated crosswise. Calcite crystals typically form in rhombohedrons, scalenohedrons, or tabular or stalactitic varieties.

USES

Calcite, a common form of calcium carbonate, has diverse uses, including construction (cement, lime, aggregate), acid neutralization (soils, wastewater), and optical instruments, as well as being a key component in the shells of marine organisms and some paints.

Industrial Applications:
Construction: Cement and Lime Production: Calcite, in the form of limestone, is a primary ingredient in the production of cement and lime, essential for building materials.
Aggregate: Crushed limestone (calcite) is used as aggregate in concrete and asphalt mixes.
Facing Stone: Marble, which is a metamorphic form of limestone (calcite), is used as a facing stone for both interiors and exteriors.

Chemical Industry:
Acid Neutralization: It has the ability to neutralize acids makes it valuable in various applications, including soil treatment, wastewater treatment, and acid mine drainage.
Flux in Metallurgy: Acts as a flux in steel production, helping to lower the melting temperature of raw materials.

Other Industrial Uses:
Paper Production: Used in paper manufacturing.
Glass Production: Used in the production of glass.
Sulfur Dioxide Removal: Used to remove sulfur dioxide from the smoke of coal power plants.
Pigment: The powder is used as a white pigment or “whiting” in paints and whitewash.
Animal Feed: Used as a dietary supplement for animals, particularly cattle and chickens, to increase calcium intake.
Food Industry: Used in the food industry.
Waste Treatment: Used in waste treatment.
Optical Instruments: Transparent calcite, known as Iceland spar, is used in optical instruments like polarizing prisms and lenses due to its unique optical properties.
Photography: Used in photography.

Scientific and Educational Applications:
Geology and Crystallography:
It is a popular mineral for demonstrating mineral properties, crystal structures, and geological processes in geology and crystallography classes. 

Other Uses:
Marine Organisms: Calcite forms the shells and skeletons of many marine organisms, including mollusks, corals, and certain types of algae.
Art and Statues: Marble, a metamorphic form of limestone, is used for statuary and carvings.
Antacids: Used in the production of antacids.
Dough Strengthener: Used as a dough strengthener.
Filter in Baking Powder: Used as a filter in baking powder.

MOHS HARDNESS

Number 3 on the Mohs hardness scale.

LUSTER

Vitreous or glassy, meaning it reflects light in a way similar to glass.

While crystalline calcite often shows a vitreous luster, massive or fine-grained forms tend to have a dull luster.

It can also exhibit resinous, waxy, or pearly luster, especially on cleavage surfaces.

CHEMICAL COMPOUND

It is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3).

WHERE TO FIND

• United States
• Canada
• Mexico
• Iceland
• England
• Germany

DIAGNOSTIC PROPERTIES

Cleavage: Exhibits perfect rhombohedral cleavage, meaning it breaks along specific planes that form rhombic shapes.
Color: Can be colorless or white, but it can also exhibit various colors like gray, red, orange, yellow, green, blue, violet, brown, or even black due to impurities.
Transparency: Can be transparent, translucent, or opaque.
Specific Gravity: Has a specific gravity of approximately 2.71.
Streak: Streak is white.

Other Characteristics:

Birefringence: Exhibits strong birefringence, meaning it can split light into two beams.
Fluorescence: Some varieties can fluoresce under ultraviolet light.
Phosphorescence and Thermoluminescence: Can also exhibit phosphorescence and thermoluminescence.
Triboluminescent: Some calcite specimens are triboluminescent, meaning they glow when scratched.
Crystal System: Belongs to the trigonal crystal system.