Both calcite and fluorite are minerals.
In order to understand the difference between calcite and fluorite, we need to dig deeper into their chemical composition and crystal structure.
In this article, you’ll learn the basics about these well-known materials and how they compare.
Calcite vs Fluorite (EXPLAINED)
As we know, there are different types of minerals.
For instance, while Calcite is a carbonate mineral, fluorite falls into the halide mineral category.
The behavioral attributes of both these minerals differ as well.
We can start with their melting points.
Calcite melts at 1612 degrees Celsius, whereas the melting point of fluorite is 1360 degrees Celsius.
The property of an element to absorb light of short wavelength and emit light of longer wavelength is known as fluorescence.
Both these minerals (calcite and fluorite) exhibit fluorescence under specific lighting.
However, fluorite also displays phosphorescence.
It is defined as the property of a substance to emit light (when it is exposed to radiation) and exhibit an afterglow after the radiation has been removed.
The chemical formula of calcite is CaCO3.
This is why calcite is also called limestone.
The chemical composition of fluorite is CaF2.
Being a halide mineral, fluorite is a type of salt.
Talking of density, fluorite is denser than calcite.
The specific gravity of fluorite is 3.19, whereas that of calcite is 2.7.
The Moh’s scale is used to measure the hardness of an element.
Fluorite is harder than calcite by one point on that scale.
It has also been observed that certain types of fluorite glow when exposed to electromagnetic energy.
This property is known as thermoluminescence.
Not only do these minerals differ in their properties, but they also look different.
For example, we can find calcite in colors such as white, yellow, red, orange, and different shades of earth.
However, fluorite is found in diverse shades of purple, golden-yellow, pink, green, blue, and brown. Interestingly, fluorite can also be colorless.
Examples of calcite include aragonite, dolomite, and soda-lime glass.
Carnallite, sedimentary rock, and NaCl Carnallite are some types of fluorite.
Why do people confuse calcite and fluorite?
Since both these minerals have similar properties and share a similar crystal system, it is natural that people often confuse them for each other.
In fact, calcite and fluorite are also mined in the same location(s) and have similar shapes as well as chemical formulas.
How to identify calcite?
Calcite is unique in the sense that it is the most stable polymorph of calcium carbonate (CaCO3).
Some other polymorphs of calcium carbonate include aragonite and vaterite.
Calcite is a common and abundant mineral.
Crystalline solids are assigned specific structural categories or types, trigonal-rhombohedral being one of them.
Calcite falls under this category of crystalline structure.
Calcite is found in different forms, such as compact, fibrous, lamellar, and granular.
Ranging from transparent to translucent, calcite has a refractive index of 1.486 to 1.498.
Another interesting thing about calcite is that it is pleochroic, which is a property of a crystal that shows different colors when viewed by light polarized in different directions.
Also, calcite is isotropic, meaning its optical values are the same when measured in different directions.
Calcite exhibits a similar structure to CaCO.
It has two Ca atoms and one CO atom.
However, the arrangement of these atoms is different.
Being the most stable polymorph of calcium carbonate, calcite is also the most common form of calcium carbonate in existence.
Calcite is available in three types of crystal structures, namely, rhombohedral, scalenohedral, and prismatic.
The most common type of calcite found on earth is rhombohedral.
These crystals are prismatic.
On the other hand, scalenohedral crystals of calcite are tabular.
Finally, as the name suggests, prismatic crystals look like prisms.
In terms of its availability (naturally), calcite is a vein mineral, meaning it has a unique sheet-like body of crystals inside a rock formation.
Another form of calcite is placer, meaning it accumulates due to gravity separation during sedimentary processes.
Where can we find calcite?
Sedimentary environments are most suitable for calcite formation.
That is why we can find calcite in shallow marine and freshwater sediments.
Carbonate sediments often have large deposits of calcite.
Magmatic environments are also known to attract calcite formation.
Molten magma results in the cementation of small grains of carbonate rocks, resulting in calcite formation.
Limestone contains large deposits of calcite.
Calcite, dolomite, and other carbonate minerals often share the space inside sedimentary rocks such as limestones.
Calcite is an important mineral for producing lime.
It is used as a flux in the production of lime, and in refining metals.
In addition, smelting of metals such as zinc, copper, and lead utilizes calcite as a flux.
Ceramic production and metal polishing are two other applications of calcite.
Another common use of calcite is to make plaster of Paris.
Given its use as a substrate material, calcite is also known as cobalt rock.
It is used to make aquariums.
Calcite finds its use as a filler in cement and plastics.
Finally, it is used as a gemstone.
How to identify fluorite?
Often, people confuse fluorite with barite, and even with a few other minerals.
Fluorite has fluorescence.
It exhibits this property under short ultraviolet light.
Minerals such as barite and calcite do not show this characteristic.
Unlike calcite (which is translucent to transparent), fluorite is transparent.
This mineral demonstrates a glassy luster and is found in a wide range of colors, such as blue, green, yellow, white, red, and pink.
However, the most common color of fluorite is blue.
Fluorite is found in several places around the world.
An interesting thing about fluorite is that it can be found in large crystals.
In fact, fluorite has been found in crystals weighing several hundred pounds.
Due to its rarity and appearance, fluorite is a collector’s favorite.
As mentioned earlier, fluorite is the mineral form of CaF2 (calcium fluoride).
When fluorite gets in contact with water (H2O), it forms a hydrofluoric acid solution.
This toxic acidic solution can burn the skin and cause strong irritation to the eyes.
Applications of fluorite include metallurgy (as flux), glass manufacturing (to make glass more transparent), and the nuclear industry.
Fluorite is used as a source of uranium and fluorine in the nuclear industry.
Lastly, fluorite also finds its use in making jewelry, clocks, and watches.
Both calcite and fluorite are important minerals, with similar, yet distinct properties.
They have important applications in different industries.
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