Blue Calcite vs. Celestite – The Similarities and Differences (With Photos)

By Keith Jackson - Geologist

| Updated

Blue Calcite vs. Celestite – The Similarities and Differences (With Photos)

By Keith Jackson - Geologist


Blue calcite and celestite are beautiful minerals that are hard to describe because of their cool, soothing blue colors. Even though they both have a beautiful color, these two minerals are different.

They come from different mineral families and have different properties and formations. Because they all have the same color palette, they are often used to make jewelry and home decor.

However, their differences show how diverse nature’s underground treasures are. As you learn more about these minerals, you’ll find a fascinating world of science and natural art.

Blue calcite and celestite have stories about how they formed deep in the Earth and reached the surface.

Blue Calcite vs. Celestite – The Major Differences

Let’s start by talking about what’s different about them. These are the ones that stand out when you put them next to each other.

Appearance – Celestite is transparent

An elegant raw natural celestite crystal
Celestite photo provided by Fine Mineral Photography – @finemineralphotography

Blue calcite and celestite look very different from one another, especially for mineral collectors and mineral enthusiasts. A cloudy, almost milky translucence is common in blue calcite, which adds to its dreamy look.

It feels smooth when you touch it, and while it can form crystals, it’s often found in masses or rhombohedral shapes. This mineral can be completely opaque or only slightly see-through. Because it’s soft, it usually has a waxy sheen that adds to its mysterious appeal.

Conversely, Celestite is the show’s star because it’s clear to see through and has beautiful, well-defined crystal shapes ranging from tabular to prismatic.

Most of the time, these crystals are bigger and stand out more than blue calcite crystals. They sparkle beautifully in any light. The color of celestite is usually more consistent, with a pale blue that can look quite intense in larger pieces.

Chemical Composition – Blue calcite is a carbonate mineral

A lovely raw natural blue calcite crystal with a smooth texture
Blue calcite photo provided by and available for purchase at vintagefairyfinds

Blue calcite and celestite are in different mineral families because their chemical makeups are very different. Calcium carbonate (CaCO3), also found in common limestone and chalk, is what blue calcite is made of.

It’s a carbonate mineral. During the formation of this mineral, calcium ions and carbonate ions come together to make its unique crystal structure.

Different impurities can make calcite different colors. For example, certain trace elements or irradiation can color it blue.

Celestite is a sulfate mineral made up of strontium sulfate (SrSO4). Strontium, a heavy alkaline earth metal, combines with sulfate compounds to make it. It’s known for having crystals that are usually orthorhombic.

This is because strontium and sulfate ions are chemically linked. Celestite’s color isn’t just caused by impurities or radiation like blue calcite’s. Tiny flaws or inclusions in the crystal lattice often cause it.

This primary difference in their chemical make-up determines their physical and optical properties and the places where they form and are most often found.

Cleavage – Celestite has perfect cleavage

Celestite photo provided by Fine Art Minerals – @fineartminerals

Blue calcite and celestite have very different cleavage, which is the tendency of minerals to break along smooth planes based on their crystal structure. This shows how differently their crystals are arranged inside.

This is what blue calcite looks like: “perfect rhombohedral cleavage.” In other words, it breaks in three directions, making a rhombohedron, a type of prism common in the calcite family.

When this mineral breaks, it usually does so along smooth, flat surfaces that reflect light evenly. This makes shiny, mirror-like planes that meet in the shape of a parallelogram.

Celestite’s cleavage, on the other hand, is very different because its crystal system is orthorhombic. It has perfect cleavage in two directions perpendicular to the crystals’ length and parallel to them.

Putting force on a piece of celestite will likely break along two planes, making rectangular or square shapes. Even though these cleavage planes are smooth, they don’t reflect light like blue calcite because the crystals are arranged differently.

Instead, celestite’s broken surfaces are more matte and have a vitreous to a pearly sheen. Gemstone cutters and collectors need to know about these cleavage properties because they affect how the stones are handled, shaped, and valued in their markets.

Density – Blue calcite has a lower density

A stunning natural blue calcite crystal cluster
Blue calcite photo provided by FreedomRock

When you compare blue calcite and celestite, their density, mass per unit volume, can tell you a lot about their chemical makeup and crystal structure. About 2.7 g/cm3 is a pretty low density for blue calcite.

This is mainly because it comprises calcium carbonate (CaCO3), which has a crystalline structure and doesn’t contain many heavy elements. Blue calcite is less dense than other carbonate minerals, which helps explain why it feels pretty light when you hold it.

Celestite has a much higher density, between 3.95 and 4.0 g/cm3. This higher density is due to its chemical makeup, strontium sulfate (SrSO4). The heavier strontium element makes the mineral heavier and more compact.

The atomic number and mass of strontium are higher than those of calcium. Because of this, celestite is naturally denser than blue calcite. You can feel this difference in density; a piece of celestite the same size as a piece of blue calcite feels much heavier.

The different densities change how the minerals feel and how they act in the environment. Celestite, denser than blue calcite, is likely to settle faster than blue calcite when these minerals are mixed with water and are part of the sedimentary process.

Celestite’s higher density can also affect how long it lasts and how it reacts to specific mechanical processes in jewelry making and other fields.

Fluorescence – Celestite does not fluoresce

A beautiful celestite crystal cluster
Celestite photo provided by EthixCrystalCo

When minerals are exposed to ultraviolet (UV) light, they give off visible light. This is called fluorescence and is caused by how their chemicals are arranged and their crystals are formed.

In this way, blue calcite and celestite are very different. It’s known that blue calcite reacts with UV light and glows blue. It can give off a red or pink glow when exposed to shortwave or sometimes longwave UV light, which is very different from its normal calm blue color.

This happens because there are impurities or flaws in the calcite molecules that soak up the UV light and then send it back out as visible light. This is called luminescence.

Celestite doesn’t usually have this fluorescent quality. It doesn’t usually glow with color when put under UV light like blue calcite does. Celestite doesn’t fluoresce because its chemicals and structure are different.

It’s not common for UV light to interact with strontium sulfate in a way that makes visible light. Even small impurities, which can make other minerals fluoresce, don’t seem to do that to celestite. This means how it reacts to UV light is a good way to tell it apart.

Price – Blue calcite is more affordable

A dazzling formation of a blue calcite chunk
Blue calcite photo provided by mkcrystalsnjewelry

Blue calcite and celestite have very different prices because of how rare they are, how much people want them, how nice they look, and how much it costs to mine them.

Blue calcite is usually thought of as an inexpensive mineral. It’s pretty common and can be found in many places worldwide, making it easier to get and lowering its market price.

The value of blue calcite can change based on the size and quality of the piece, but because there is so much of it available, prices tend to stay low.

Because it’s cheap, blue calcite is popular for people just starting to collect stones and those interested in crystal healing or decorative stones.

Celestite usually sells for more money on the market. Celestite isn’t one of the most expensive minerals, but its price is affected by how rare it is and how much people want to buy its beautiful naturally formed crystal clusters.

The value goes up a lot for specimens that are clear and have a deep, vivid blue color, or for specimens that form beautiful, one-of-a-kind crystal clusters. Celestite’s price can also be affected by where it’s mined.

Crystals from certain places may be more valuable because of their size, color, or clarity. Extracting celestite can be more complex, and its sites are not as spread out as blue calcite, which add to its high price.

Celestite vs. Blue Calcite- The Similarities

They’re not the same, but they are alike in some ways. The unique world of gemstones is more fun to enjoy when we know what they all have in common.

Color – Both celestite and blue calcite have blue hues

A stunning sphere-shaped piece of celestite mineral
Celestite photo provided by Cristais

The color of blue calcite and celestite is very similar. Shades of calm blue make them very popular in the mineral world.

This standard range of blue colors, from soft to bright, often creates a relaxing and soothing look that collectors and people interested in the metaphysical properties of crystals like.

In calcite, the blue is usually soft and cloudy, and sometimes hints of white or light gray make it look a bit ethereal. This color can be different from one specimen to the next.

Some may be a very pale blue that looks almost clear, while others may be a more bottomless sky blue. Blue calcite usually gets its color from microscopic inclusions or irradiation, which changes the crystal’s ability to absorb light in small ways.

Celestite is also blue, but its color is more consistent and ranges from pale blue to blue-gray. The crystal lattice usually has small amounts of gold or other impurities that give it its unique blue color.

Celestite can sometimes be found in shades close to a deep, celestial blue. These specimens are usually more valuable because of this.

People usually think of celestite as having a more even color throughout the crystal, while blue calcite can look more “swirled” because its translucency varies.

Conductivity – Blue calcite and celestite are poor conductors

Blue calcite geode with bubble-like crystals
Blue calcite photo provided by SunshineTrailCanada

Because they are both non-metallic minerals, blue calcite and celestite have similar electrical properties regarding conductivity. Conductivity is a measure of how well minerals can move electricity.

Both blue calcite and celestite have very low conductivity. This often happens with insulating materials, like most non-metallic minerals, because they don’t have free electrons or charged ions that can move through them. These are needed for materials to conduct electricity.

Neither of their chemical composition is good at carrying electricity because the way their atoms are arranged doesn’t let electrons move freely, which is needed for electricity to flow. Instead, the electrons are tightly bound within the mineral lattice.

This makes it hard for them to move, which makes it harder for the material to conduct electricity.

It’s hard for heat energy to pass through them because of how their crystal lattices are set up. The atoms absorb energy and make the lattice vibrate instead of moving through the material.

Formation – Celestite and blue calcite form in sedimentary rocks

A stunning celestite geode with big crystals inside
Celestite photo provided by NewMoonBeginnings

Even though they are different, blue calcite and celestite are often formed in sedimentary environments, which is another way they are similar.

These minerals usually form when mineral-rich water condenses, which happens most often in places where the right mix of chemical elements is present.

Blue calcite is calcium carbonate that usually forms in shallow water. It’s a common part of limestone and is made when calcium ions and bicarbonate ions in seawater settle together chemically.

Living things can speed up this process, which is why calcite is often found in sedimentary rock layers formed in ancient seas. It can also form as stalactites and stalagmites in caves when calcium-rich water drips and causes it to slowly solidify.

Celestite, which is made up of strontium sulfate, also forms by sedimentation. It’s usually found in gypsum and limestone formations or dolostones where celestine has replaced calcium carbonate.

It forms from water, usually in an evaporative environment like the ocean or a lakebed, where strontium-rich water mixes with sulfate ions to make celestite crystals. In addition, it can happen in hydrothermal veins and cavities of sedimentary rocks, especially if the rock has been changed after it was formed.

Hardness – Both blue calcite and celestite are soft minerals

A raw blue calcite mineral with a mesmerizing deep blue color
Blue calcite photo provided by RockyMountainsDruid

The hardness of blue calcite and celestite is similar. A mineral’s hardness is how well it resists scratching. Both minerals are in the lower range based on the Mohs scale, which measures this quality.

About 3 on the Mohs scale is how hard blue calcite is, which means it’s soft. This means that harder things can scratch it easily.

It’s soft because the bonds between the calcium and carbonate in its molecular structure are not as strong as in some other minerals. This trait is expected in the calcite family, so calcite is often found in the earth as a powder.

Celestite has a hardness of about 3 to 3.5, a little higher on the Mohs scale. Even though this is harder than blue calcite, it’s still a soft mineral that can be scratched by harder things.

Celestite is very fragile because its crystal structure, which comprises strontium and sulfate, is quite brittle.

Because blue calcite and celestite are both pretty soft, they are easy to scratch or damage if you are not careful. In addition, it changes how they are used in real life.

For example, because they are soft, they can’t be used in all jewelry designs, especially ones that need to last a long time. But because they aren’t too hard, they are great for carving or using as decorations.

Location – Celestite and blue calcite can be found in global localities

A radiant raw celestite crystal with clear blue crystals
Celestite photo provided by TheMysticalMandala

Even though blue calcite and celestite have different chemical makes-ups and some physical traits, you can find them in similar places worldwide. This is mostly because they both form in sedimentary environments shared globally.

There are a lot of blue calcite deposits all over the world. Mexico is a notable place where it can be found in large numbers, as are many places in the United States, especially in states like Florida and Arizona.

It can also be found worldwide, from South America to Africa, as long as the sedimentary geology is right.

Celestite can be found in many places around the world, though it’s not as common as blue calcite. Madagascar has large deposits. Madagascar is famous for its big, high-quality crystals.

The mineral can also be found in Italy, Britain, Egypt, and the United States, especially around the Great Lakes. Like blue calcite, celestite is usually found in sedimentary rock layers, often with other minerals like gypsum and halite.

The places where you find these rocks can tell you about their history. It’s exciting to find blue calcite and celestite; these are the best rockhounding places to look!

Luster – Blue calcite and celestite have vitreous luster

A stunning polished and tumbled blue calcite stone free form
Blue calcite photo provided by FreedomRocksCo

It’s said that blue calcite and celestite have the same luster, which is how light moves across the surface of a mineral. These minerals have a vitreous to pearly luster, making them look like glass. This is especially clear when they’re polished.

People often say that the shine of blue calcite is vitreous to resinous because it reflects light like glass or resin. Blue calcite can get a beautiful shine when cut and polished, making it look better.

But the crystal’s shine can look dull if its surface is rough or natural, which happens often with unpolished specimens.

Celestite usually has a vitreous luster that looks like broken glass. Celestite specimens of the highest quality can have a very bright sheen, which makes them very popular with collectors.

When the crystals are well-formed and free of impurities, their natural facets can shine with a brightness that brings out their natural beauty.

The similar sheens of these two minerals make them more valuable as decorative items, especially to collectors and fans. They are beautiful, and how they catch and reflect light also helps you figure out what minerals they are.

Even though they have a similar sheen, the two are usually easy to tell apart by color and crystal structure. But they all have the same vitreous to pearly shine, which makes them valuable and appealing in many situations, from making jewelry to decorating your home.

Magnetism – Neither celestite nor blue calcite is magnetic

An egg-shaped polished celestite free form
Celestite photo provided by DreamPieceByErin

Regarding magnetism, blue calcite and celestite have a lot in common. They are both pretty much non-magnetic. Minerals are magnetic if they have iron, nickel, or cobalt in their crystal structure and how they interact.

However, neither blue calcite nor celestite has these elements in enough of quantity to be magnetic.

Blue calcite doesn’t have many ferromagnetic or ferrimagnetic materials in it. As a result, it doesn’t react strongly to magnetic fields. This means that it won’t stick to magnets and doesn’t keep its magnetic properties when exposed to one.

This is normal for most carbonate minerals unless they have mixed magnetic minerals, which blue calcite doesn’t usually have.

In the same way, celestite does not contain any elements that are known to be magnetic. Celestite is not magnetic because its crystal structure has no iron, nickel, or cobalt.

Magnets won’t pull on or pull it toward magnets, and it doesn’t become magnetized in a magnetic field like blue calcite.

Streak – Both blue calcite and celestite have a white streak

A gorgeous raw blue calcite mineral
Blue calcite photo provided by SoulswithHeart

When you rub a mineral against an unglazed porcelain surface, called a streak plate, you can see that blue calcite and celestite have similar streaks.

This is one of the most important ways to tell them apart. The mineral’s name can be guessed from the color of the powder left behind, called the “streak.”

Blue calcite leaves a white streak on a streak plate, even though it is usually blue in hand specimens. This is because the mineral’s color comes from microscopic impurities or inclusions, while the streak test shows the mineral’s color when it’s powdered.

Because calcite is mostly calcium carbonate, it’s colorless when powdered, leaving a white streak.

In the same way, celestite also has a white streak, no matter how blue it is when it’s in crystal form. The mineral strontium sulfate shows its true color when ground into a fine powder.

This is because the powder has no impurities or structural features that give the crystal its blue color.

The Easiest Ways To Tell Blue Calcite and Celestite Apart

Comparison of blue calcite and celestite beside each other
Blue Calcite at the top and Celestite at the bottom

There are a few ways to tell the difference between blue calcite and celestite. It’s enjoyable to try to recognize what makes them special. You should know that even though they look alike, they are not the same in some important ways.

Feel to the touch

Hardness is a property of minerals that tells you how easy they are to scratch. It’s not very hard to say that blue calcite is soft. You could likely scratch it if you used a regular nail.

Even though it’s not as soft as blue calcite, celestite is still pretty soft. On the other hand, it would be harder to scratch celestite with a nail than blue calcite.

Observe the shape of their crystals

Blue calcite can be found in many different shapes, but most of the time it’s in smooth, round masses. Very rarely does it turn into clear crystals that you can see.

Celestite, on the other hand, is famous for having beautiful crystals that are well-formed. As they grow, they often take on cool shapes, such as long prisms or flat, tabular crystals. This can help you tell the difference between celestite and blue calcite.

Perform a streak test

A small amount of mineral powder is left behind when you rub it against a piece of unglazed porcelain tile.

Although both blue calcite and celestite leave a white streak, blue calcite is softer and leaves a streak more easily.

About Keith Jackson - Geologist

Keith Jackson is an avid rockhound who is constantly exploring new sites to expand his collection. He is an active Geologist with a wealth of experience and information from across the country that he loves to share with the Rock Chasing crew.

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