Fluorite is one of the gemstones that’s often mistaken for calcite and vice versa. If you know a little about crystals, you might know that even though fluorite and calcite share some traits, there are key differences between the two.
But did you know that there are 11 tell-tale differences between fluorite and calcite? If you want to know what these are and pick up some tips along the way, then this is the blog post for you.
In this article, you’ll get 11 differences between fluorite and calcite, and discover a little about both crystals.
The differences between fluorite and calcite:
Fluorite and calcite are different crystals
Fluorite is a halide crystal that’s classed as semi-precious, but calcite is a calcium carbonate crystal that’s classed as a common mineral.
Fluorite and calcite are made up of different elements. Calcite is calcium carbonate (CaCO3), which consists of calcium, carbon, and oxygen. But fluorite (CaF2) is made up of calcium and fluorine.
Fluorite brings focus and calcite energizes
Fluorite and calcite both have healing and metaphysical properties when you use or wear them, but each one brings different gifts. Fluorite mostly brings calm and focus, while calcite energizes you and boosts creativity.
Fluorite’s gifts depend on the color, but the crystal is believed to bring mental clarity, focus, and better concentration. It also enhances learning and memory, and helps you make better decisions and solve problems.
Calcite is believed to amplify energy, promote emotional balance, enhance creativity and intuition, and help with physical healing based on spiritual and energy healing rituals.
Fluorite and calcite are often found in different countries
Fluorite and calcite are both common minerals found in many countries around the world, although specific mining locations can vary. Fluorite and calcite can occur together in some geological settings.
Some of the largest deposits of fluorite are in China, Mexico, Mongolia, South Africa, and Spain. And some of the biggest calcite deposits are in Italy, Mexico, and the United States. Calcite is more widely available and abundant than fluorite.
Below is a table showing the abundance of fluorite and calcite in different countries:
Note that the categorization of “abundance” is subjective and depends on the source or location within a country. This table isn’t an exhaustive list of all the countries where fluorite and calcite are found, but rather a selection of some countries with notable deposits of these minerals.
Fluorite is more expensive than calcite
On average, fluorite is more expensive than calcite because fluorite is rarer and is often found in smaller quantities and in more difficult-to-reach locations.
Calcite is mainly used as a decorative mineral and not as a gemstone, so it’s sold by weight or size, not carat. The price depends on factors like the size, quality, color, and source.
Fluorite that’s used for decorative purposes is also usually sold by weight or by size, with prices depending on the size, quality, rarity, etc. Fluorite can also be used in jewelry and is often sold in carats (cts), a weight measurement for gemstones.
Fluorite is harder than calcite
The Mohs scale ranks how hard minerals are based on what can scratch them and what they can scratch. There are 10 minerals on this scale, each with a hardness rating from 1 (softest) to 10 (hardest). Minerals with a higher rating can scratch those with a lower rating but not the other way round.
Fluorite has a Mohs hardness of 4, so it’s not very hard or durable. But calcite only has a Mohs rating of 3, so it’s even softer and this is one of the ways to tell real calcite from fake. Fluorite can scratch calcite but calcite cannot scratch fluorite.
Colored fluorite is more common but calcite is mostly clear
Fluorite is usually purple, but it also comes in pink, blue, green, yellow, orange, brown, black, and clear or colorless. There’s even a rainbow crystal with multiple colors.
But most calcite is white or colorless, even though it can be found in other colors.
Fluorite is found in veins but calcite forms with precipitation
Fluorite is most commonly found in hydrothermal veins, while calcite is usually in sedimentary, metamorphic, and igneous rocks. Sometimes the crystals are found together, but this isn’t the norm.
Here’s how each of these crystals formed…
How fluorite forms
Millions of years ago, hot liquids flowed through cracks and fractures in the Earth’s crust. These fluids usually came from volcanos or were heated groundwater, and they carried dissolved minerals in them.
As these fluids cooled and pressure changes occurred, the minerals in the fluid crystallized and created veins of crystals. Fluorite formed in these veins over long periods of time.
But fluorite also formed in sedimentary rocks or as a secondary mineral in granite, pegmatites, and other igneous rocks.
How calcite forms
Calcite is usually formed on one of two ways:
- Chemical precipitation
When water has a high concentration of calcium and carbonate ions, they sometimes combine and form a solid mineral called calcium carbonate. This process is called precipitation.
When the calcium carbonate forms hexagons, it becomes the crystal known as calcite. This can occur in different areas and under different environmental conditions.
2. Biological precipitation
In biological precipitation, marine organisms extract calcium and carbonate ions from seawater to build their shells and skeletons.
Over time, the concentration of calcium carbonate increases and calcite crystals form, along with rocks such as limestone and chalk, which are mainly made of calcium carbonate.
Fluorite has 4 break lines and calcite has 3
When put under pressure, some crystals make clean, predictable breaks.
When we can predict where a flat surface of a crystal will break under pressure, we call it a cleavage plane. Cleavage planes are set by the crystal’s structure, and different crystals have different cleavage planes (if they have any at all).
Cleavage planes are so reliable that we can even use them to identify crystals.
When put under pressure, fluorite breaks off perfectly along four cleavage planes or lines, while calcite breaks along three lines. Also, fluorite reliably makes clean breaks along its cleavage planes every time, but calcite is sometimes a little less than perfect in its breaks.
Fluorite and calcite have different crystal systems
There are seven types of crystal systems that we know of, and each system gives the crystal a different shape when it forms.
Fluorite belongs to the cubic crystal system, while calcite has a trigonal crystal system. This gives raw fluorite tightly packed cubes and makes it more rectangular than calcite, which has stretched-out cubes with six sides (a rhombohedral shape).
Fluorite and the cubic crystal system
In the cubic crystal system, crystals have a symmetrical shape with equally sized faces. The crystal structure is made up of tightly packed cubes.
These cubes are often slightly lengthened, giving raw fluorite a more rectangular look than calcite.
Calcite and the trigonal crystal system
In the trigonal crystal system, crystals have threefold symmetry and are asymmetrical.
Calcite crystals typically have a rhombohedral shape, so they look like a stretched-out cube with three cleavage planes.
The crystal faces may be curved or flattened, which means it comes in a variety of shapes such as rhombohedrons (six sides) and prisms with flat or pointed ends.
In general, calcite crystals have a geometric, angular appearance with sharp edges and flat faces, but their exact shape depends on the conditions under which they formed.
Fluorite is denser than calcite
The density of a crystal is how heavy it is compared to how big it is.
Fluorite is denser than calcite, with a specific gravity of 3.18, while calcite has a specific gravity of 2.71. This means that fluorite has more minerals or elements in it than calcite and so it’s heavier than calcite, even when it’s the same size.
Imagine you have two of the same boxes. One is full of feathers and the other is full of rocks. Even though the boxes are the same size, the one with the rocks is much heavier than the box with the feathers because the rocks are denser than the feathers.
The same thing is true for crystals. Some crystals are denser because they have more elements packed into them, even if they’re the same size as other crystals. We measure how dense a crystal is by weighing it and seeing how big it is, then seeing how much water it displaces in a beaker.
Calcite fizzes in hydrochloric acid
If you pour hydrochloric acid over calcite, the crystal produces carbon dioxide bubbles and fizzes. But pour hydrochloric acid over fluorite and there’s no reaction.
This happens because fluorite and calcite have different chemical compositions. Fluorite is made up of calcium fluoride, while calcite is made up of calcium carbonate. These different chemical compositions result in different reactions when exposed to the acid.