Calcite

Calcite is a rock-forming mineral with a chemical formula of CaCO3. It is extremely common and found throughout the world in sedimentary, metamorphic, and igneous rocks. The most common form of calcium carbonate, calcite is known for the variety and beautiful development of its crystals. These occur most often as scalenohedra and are commonly twinned, sometimes forming heart-shaped, butterfly twins. Crystals with rhombohedral terminations are also common; those with shallow rhombohedral terminations are called nailhead spar. Highly transparent calcite is called optical spar. Although calcite can form spectacular crystals, it is usually massive, occurring either as marble (p.301) or as limestone (p.319). It is also found as fibers, nodules, stalactites, and earthy aggregates. Calcite specimens can occur in metamorphic deposits, igneous rocks, and hydrothermal veins.

• Some geologists consider it to be a “ubiquitous mineral” – one that is found everywhere.
• Calcite is the principal constituent of limestone and marble. These rocks are extremely common and make up a significant portion of Earth’s crust.
• The properties of calcite make it one of the most widely used minerals. It is used as a construction material, abrasive, agricultural soil treatment, construction aggregate, pigment, pharmaceutical and more.

Name: From the Latin calx, for burnt lime, an allusion to an important commercial use.

Association: Dolomite, celestine, fluorite, barite, pyrite, marcasite, sphalerite (low-temperature veins); zeolites, chalcedony, “chlorite” (vesicles); talc, tremolite, grossular, quartz (metamorphic); nepheline, diopside, apatite, orthoclase (igneous).

Polymorphism & Series: Trimorphous with aragonite and vaterite; forms a series with rhodochrosite.

Mineral Group: Calcite group

Composition: Calcium carbonate, CaC03. CaO = 56.0 per cent, C02 = 44.0 per cent. Small amounts of magnesium, ferrous iron, manganese, and zinc may replace the calcium.

Diagnostic Features: Distinguished by its softness (3), its perfect cleavage, light color, vitreous luster. Distinguished from dolomite by the fact that fragments of calcite effervesce freely in cold hydrochloric acid, whereas those of dolomite do not. Distinguished from aragonite by having lower specific gravity and rhombohedral cleavage.

Chemical Properties

Chemical Classification	Carbonate Mineral
Formula	CaCO3.
Common Impurities	Mn, Fe, Zn, Co, Ba, Sr, Mg, Cu, Al, Ni, V, Cr, Mo, Pb

Calcite Physical Properties

Color	Usually white but also colorless, gray, red, green, blue, yellow, brown, orange.
Streak	White.
Luster	Vitreous.
Cleavage	Perfect, rhombohedral, three directions.
Diaphaneity	Transparent to translucent.
Mohs Hardness	3
Crystal System	Hexagonal
Tenacity	Brittle
Density	2.7102(2) g/cm3 (Measured)    2.711 g/cm3 (Calculated)
Fracture	Conchoidal
Parting	Readily along twin lamellae {0112} and {0001}.

Calcite Optical Properties

RI values:	nω = 1.640 – 1.660 nε = 1.486
Twinning	At least four twin laws have been described, the most common being when the twin plane and the composition plane are {0112}. Also common with twinning on {0001} with {0001} as the compositional surface, producing re-entrant angles. Uncommon with {1011} or {0221} as twin planes, producing somewhat heart-shaped crystals (“butterfly” twins).
Optic Sign	Uniaxial (-)
Birefringence	δ = 0.154 – 0.174
Relief	Low
Optical Extinction	Symmetrical to cleavage traces.

Occurrence of Calcite

Calcite most commonly occurs in sedimentary settings, particularly in shallow marine settings as the shells and hard parts of marine organisms.

It is also found in hydrothermal veins and hot spring deposits.

In sedimentary environments, calcite most often occurs as limestone rock or as marble, which is metamorphosed limestone.

Calcite is often the only mineral present, but in some sedimentary environments, calcite may be associated with dolomite, gypsum, anhydrite, chert, or halite.

In hydrothermal veins, quartz and other common vein minerals such as pyrite, dolomite, fluorite, galena, and chalcopyrite may occur with calcite (Kauwenbergh, 2010) .

Distribution

Country’s of origin for calcite are: ALMOST EVERY CONTINENT!!! Large deposits of brightly colored calcites occur in Mexico and the USA

Calcite is distributed in the following places:

• Iceland – At the Helgustadanama mine, Reydarfjord.
• England – From Alston Moor, Egremont, and Frizington, Cumbria; Weardale, Durham; at Liskeard, Cornwall,
• Germany – From St. Andreasberg, Harz Mountains, and Freiberg, Saxony,
• Namibia – From Tsumeb,
• Congo – In the Mupine mine, Katanga Province,
• Romania – At Herja (Kisbanya), Baia Mare (Nagybanya) district,
• Russia – At Dalnegorsk, Primorskiy Krai.

Calcite Production

Step 1: The incoming minerals are pulverized and transferred to ball mills.

Step 2: These powders, which are crushed by the balls as they are in the cement factories, are also sieved from the sieves and separated into the desired grades.

Step 3: Thus, 3-micron, 5-micron, 10- micron bags are sold separately.

The important issue here is that 100 tons of mine becomes 99.99 tons without any additives.

In other words, there is no decrease in the mine, nor is there any contribution.

Uses in Industry of Calcite

Paper Industry

• It is used as filler and coating material.
• Thus, the surface is hardened, smoothed and color harmonized.
• Other chemical values will vary depending on the paper type.
• It allows rapid drying of the paper due to the oil absorption feature (Şahin, 1999).
• Thus it is used in newspaper, magazine and quality paper production.
• It is used as a filling material on cigarette paper.

Paint Industry

• Used to be cheap.
• It is used to replace pigment material and prevent steel wear.
• It provides increased resistance to water and chemicals.

Tire (wheel) Industry

• Used as filler material.
• It should be less than 20 micron and rounded.
• It should be well dispersed in rubber paste.
• Allows the tire to be used for a long time without suffering loss of softness. So there is no elongation and stretching.

Plastic Industry

• It is used as a filling material since it easily comes out of the mold and allows the thickness to be the same everywhere (Şahin, 1999).
• Provides hardness and flexibility at the same time.
• It is resistant to high temperature.
• It should be 3.0 – 0.02 microns in size and rounded.

Animal Feed

• It is used as a filling material because it allows the growth of bones and teeth of animals.
• CaCO3 must be at least 92%, SiO2 must be quite low and elements such as As-F must be in certain proportions.
• It should be smaller than 400 microns for chick feed, 3 mm for large poultry and 25 microns for large animals (Şahin, 1999).

Agriculture

• In order to obtain good and abundant products from acid-bearing soil, it is necessary to give Ca in abundant quantity.
• Thus, the life of the organisms in the earth is improved and the pH is 6-7,5.
• Marble tobacco or limestone is used as fertilizer instead of Ca salts which are lost to planted soil.

Glass-Glass Glue

• Increases resistance to chemical effects.(in glass)
• Because it opens the color of the glass, it is generally used for making bottles and window glass.(in glass)
• Since cryptocrystaline has the structure, oil absorption is very high.(in glass glue)
• Used as filler material.(in glass glue)
• The finely ground limestone is also used for the same purpose.(in glass glue)

Ceramic Industry

• The harmful effects of SiO2 in the medium are removed by adding it to the tile slurry.
• Usage rate is 2-6%. If this ratio is exceeded, the color will become pink, yellow speckles will form and deform at high temperatures.
• CaO increases the strength of the ceramic material.

Water Treatment

• It ensures that the hardness of the water is removed.
• It is used in the control of water color and cleaning of water.

Coal Mine

• It is used to prevent the explosion of coal dust and the spread of flame from explosives.
• The size should be -84 microns and in the form of powder which does not make cake when heated.

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.
• Modern construction uses calcite in the form of limestone and marble to produce cement and concrete.
• These materials are easily mixed, transported, and placed in the form of a slurry that will harden into a durable construction material.
• Concrete is used to make buildings, highways, bridges, walls, and many other structures.

The Other Sector

The Other Sectors

• Medicine.
• Sugar: During the production of sugar, the pollutants separate from the sherbet.
• Cosmetic.
• Explosive.
• Joint material.
• Oil refineries.
• Wire production.
• Leather sector: It is used to remove  animal hair.

The Geologic Importance of Calcite

• All natural waters contain dissolved calcium and carbon dioxide, and their concentration is especially high in seawater.
• Many marine animals including corals, snails, clams, algae, and microscopic plankton use calcite and aragonite to form their shells and hard parts.
• Microorganisms can also indirectly lead to the precipitation of calcite as they alter the chemistry of the fluids in which they live.
• Once formed, calcite is easily dissolved and its component ions released to precipitate elsewhere.
• As a consequence, calcite is not only the main mineral of limestone rocks and marble (metamorphosed limestone), but also a common accessory component of sandstone and siltstone rocks.

References

• Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
• Dana, J. D. (1864). Manual of Mineralogy… Wiley.
• Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
• Mindat.org. (2019): Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].
• Kauwenbergh, S. J. Van (2010). World Phosphate Rock Reserves and Resources. Muscle Scholas, Alabama 35662. U.S.A. IDFC.
• Palache, C., H. Berman, and C. Frondel (1951). Dana’s system of mineralogy, (7th edition).
• Şahin, N., (1999). ‘Endüstriyel Hammadde Olarak Kalsit (CaCO3) ve Cevher Hazırlaması’. MTA Genel Müdürlüğü Derleme Rap No:10294, Ankara.
• Yavuz, A.B. ; Türk, N. ; Koca, M.Y. (2002). The Mineralogical, Chemical, Physical and Mechanical Properties Of Muğla Region Marbles. Geological Engineering Research Article. 28(1).