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Many people use the terms rock, mineral, crystal, stone, and gemstone interchangeably, but these terms actually have specific meanings in the world of rockhounds and gem collectors. While there is some overlap between them, knowing the difference is crucial for a passing knowledge of gemology or mineralogy.
A rock is any two or more minerals bonded together, while a mineral is a naturally occurring inorganic element. A crystal refers to the structure of a mineral, and there are many different kinds of crystalline structures. A mineral can be part of a rock, and a crystal can be a mineral, but the terms are not synonymous.
Even though they’re all referring to the same types of inorganic matter, it’s important to know the differences between rocks, minerals, and crystals. Read on to learn more about these materials and how their differences pertain to rock and gem collecting.
If you are interested in checking out the best books about rockhounding and identifying rocks, minerals, and crystals you can find them by clicking here (Amazon link).
What is a Rock?
In geology, a rock occurs when any two or more types of minerals become aggregated together, forming a single solid comprised of several mineral types.
Rocks are one of the major components of the Earth’s outer layer, and eventually, break down to form both sand and soil. In the gem and rock world, the people who study rocks specifically follow a path of study called petrology.
There are there major categories of rocks:
These rocks are formed by the compression of sediment in the Earth’s oceans over several thousands of years. A few varieties of common sedimentary rock include limestone, sandstone, and shale.
Geologists can determine the age of a piece of land by studying the layers of sedimentary rock it contains.
Volcanic eruptions form igneous rocks. When lava erupts from a volcano and runs down the mountainside, it eventually cools into igneous rock.
Some common types of igneous rock include granite, basalt, and pumice. Volcanic eruptions are also the source of volcanic glass, which is known as obsidian.
- Metamorphic rocks:
Metamorphic rocks are created by a variety of powerful geological forces such as intense pressure or heat in the Earth’s crust. Common forms of metamorphic rock that are used in human construction are marble, soapstone, slate, and schist.
While they may not seem that important, rocks form an important part of Earth’s ecosystems since it is the breakdown of rock that ultimately leads to friable topsoil.
Without rock or some other hard mineral to break up the soil, many plants cannot gain access to the oxygen and water that they need to survive. Areas of dirt with very little friable soil, such as hardpan, are extremely hostile habitats for animals to survive in as well.
What is a Mineral?
A mineral is a type of inorganic material that makes up rocks. While rock is made up of various minerals mashed together into an aggregated solid form, minerals are individual elements that have the same atomic structure through and through.
There are tons of minerals in the natural world, and each of them has very different properties when exposed to different environmental parameters.
Here are the different qualities that determine what a mineral is:
- It occurs in the natural world.
There are synthesized materials that are similar in chemical structure or properties to naturally occurring minerals, but to be defined as a mineral, a substance must be found in nature.
- It is inorganic:
Minerals are inorganic compounds, which means that they’re neither biological nor are they the result of a biological operation.
Instead, minerals either act upon the natural world (such as a rockslide) or are acted upon (such as when an animal digs a burrow or makes a rock into a tool).
- It is solid:
All minerals, by definition, are solid-state matter. This means that minerals in a gas, plasma, or liquid state do not exist except as a compound.
It has a stable chemical composition:
A mineral can be categorized and labeled because it has common features regardless of where it is found. For example, if you examine the molecular structure of fluorite in one crystal specimen and the molecular structure of fluorite in another, the molecular structure of the two pieces of fluorite will be identical, even if the outer appearance of the crystals varies.
It has an organized internal structure: The molecules and atoms of a mineral have a stable and repeating pattern, which is why minerals often take on a defined crystalline structure.
The order of the atoms ends up showing in the resulting mineral’s outward physical appearance as well as in its molecular structure.
People also mean different things when they say mineral, depending on the context of the conversation. For example, geologists have a very different idea of what minerals are than nutritionists do.
Nutritionists deal specifically with minerals that are important for human health, while the older meaning of the term is taxonomical.
Before the adoption of formalized taxonomy for plants and animals, things were broken down into simple categories of animal, mineral, or vegetable.
TIP: Double refraction or birefringence is a typical physical property for a lot of minerals. Find out eight common minerals that show double reflection in the article below:
8 Minerals That Show Double Refraction (+ Explanation Why)
What is a Crystal?
When people say “crystal,” they’re usually referring to a mineral that has taken a crystalline form. A crystal is simply a mineral that stands alone as a single structure versus being integrated into an aggregated solid like a rock.
The atoms in a crystal are created along a very strict structural lattice, leading to the resulting solid having a geometric, almost inorganic shape.
Human cultures have long prized crystals, and even in the modern-day, many crystals are still regarded to have metaphysical properties such as the ability to attract love or abundance into the life of its owner if worn or displayed.
Crystals are also commonly used in religious rites, especially in polytheistic or pagan religions such as Wicca and other New Age movements.
While the magical properties of crystals remain a matter of debate, the idea that crystals give off vibrations is a physical truth.
Each type of crystal vibrates at slightly different frequencies based on its different molecular structures. It is these “good vibrations” that New Age practitioners associate with positive life changes.
However, the vibrations in crystals are also applicable to real practical science. By studying the vibrations of crystals and learning how to control them, chemists and geologists are learning how to make electronic devices that depend on these minerals more energy efficient.
BTW: Do you want to know more about rock and mineral identification? The books listed below are the best ones you can find on the internet (Amazon links):
- Smithsonian Handbooks: Rocks & Minerals
- Gemstone & Crystal Properties (Quick Study Home)
- Ultimate Explorer Field Guide: Rocks and Minerals (National Geographic Kids)
Differences Between Rocks, Minerals, and Crystals
There is some overlap between rocks, minerals, and crystals, but their differences largely define them. Here are some of the major differences between the three:
Rocks can be made of minerals or crystals but cannot typically be formed by a single mineral except in monomineralic rocks, which are almost unheard of in the natural world.
Rocks can contain crystalline minerals, but typically also contain other solid-state molecular structures as well. This may lead to the crystal in a rock appearing either studded into other types of rock or isolated as a geode.
Minerals make up both rocks and crystals. The word “mineral” can also be used to describe a taxonomical category or a specific set of minerals that are ingested in food and drink to form part of a human’s nutritional profile.
Crystals can be features in a rock but are created by a single mineral rather than many. Crystals also feature a specific type of molecular structure that results in rigid geometric patterns.
Minerals and rocks, on the other hand, can encompass a wide variety of different physical appearances and colorations. The word “crystal” refers to both a mineral with a crystalline appearance as well as the molecular structure of a crystal itself.
When it comes to the hobby of rock and gem collecting, these three terms generally refer to the same types of specimens for sale.
The only difference is their geological and scientific categorization. If you want a high-quality specimen when you’re looking to expand your collection, you’ll want to look under each term for the broadest selection of potential buys.
It’s also good to have a general idea of what kind of crystals, minerals, or rocks you specifically want. A rockhound can collect all three.
TIP: If you already own a huge rock collection but you want to start to collect new minerals or crystals, read these helpful tips on what to do with your old rock collection:
What To Do With Old Rock Collection? 3 Simple & Practical Ideas
Can a Rock Be Made of One Mineral?
A rock cannot be made of a single mineral by its traditional definition. When you see a rock made of a single mineral, this rock usually has a crystalline structure and is referred to as a crystal, not a rock.
However, rocks that do only contain one mineral are known as monomineralic. There is no naturally occurring monomineralic rock that is completely pure through and through.
The monomineralic rocks are marble, dunite, and anorthosite. Marble has been a popular building material for hundreds of years due to its unique coloration, and anorthosite is a monomineralic rock that is found more often on the moon’s surface than it is on the Earth’s.
Dunite is a monomineralic rock that is over 90% pure. This substance is found more often deep in the Earth’s crust than near the topsoil and is sought after by industries for its engineering applications, particularly the refraction of light.
Here are some of the other minerals that are found that are monomineralic, despite being not being purely monomineralic:
- Chalk limestone
Most of the monomineralic rocks found that aren’t pure are still very rare in nature, and most are difficult to find.
Are All Minerals Crystals?
Yes! All minerals are crystals (because they all contain a crystalline atomic structure), and all crystals are formed from minerals. So if you see crystals for sale or minerals for sale, you can pretty much expect the same sorts of specimens to be available.
Unlike minerals, however, crystals can form from either an inorganic substance or an organic substance, such as plant-derived sugar.
Crystal is just a type of atomic structure that is sometimes reflected in the outward appearance of the object. Most minerals do occur naturally as some kind of crystal.
Minerals and crystals are both used in jewelry-making, and any rock can be carved into a crystalline shape. When a mineral is deemed to have aesthetic value and is faceted like a jewel, this kind of rock is called a gemstone rather than a crystal.
The crystalline structure of a gemstone isn’t its natural internal structure; it’s a geometric pattern created by the jeweler.
Crystals such as fluorite and quartz are usually categorized under what rockhounds typically consider semiprecious stones.
These minerals are beautiful and can make great additions to any rockhound’s collection, but typically aren’t as high in value as gemstones like sapphires or rubies. Nevertheless, some semiprecious, such as ammolite or red beryl, are very rare.
TIP: Minerals’ streak is one of the most important tests for mineral identification, especially while working with native metals and sulfide minerals. Check out the complete guide on testing mineral’s streak:
DIY Guide: Testing Mineral’s Streak (Explained by Expert)
Special Forms of Minerals and Crystals
There are so many minerals that form different crystals that it’s impossible to find two that look exactly alike despite their similar chemical composition.
Here are some of the most interesting forms of minerals and crystals that you can find and some intriguing qualities of them:
Fluorite comes in a wide range of colors, but pure fluorite is completely clear. The color instead comes from the way that fluorite’s crystalline structure bends and refracts light as it bounces through the mineral.
- Sunstone (Iceland spar):
The sunstone was a crystal that was used by the ancient Vikings as a way to navigate their way to the New World and is formed from a specific crystalline form of calcite.
Iceland spar refracts light twice, allowing navigators to line it up with the sun and the horizon to find their way across the ocean.
Quartz is most famous for its ability to generate electricity, which is why it has been included in watchmaking and clockmaking activities for hundreds of years.
Quartz crystals are also the mineral that scientists used to analyze and eventually decipher the shape of atomic crystalline structures.
The interesting thing about autunite other than its weird scale-like shape and yellow coloring is that it is luminescent under ultraviolet lighting, which is a fancy way of saying it glows under blacklights.
This fluorescent glow is caused by the subatomic movement of the autunite participles in response to the energy being delivered by ultraviolet rays.
One odd property that some crystals and minerals contain is the ability to change color according to their exposure to light. Hackmanite is one such crystal, appearing to be pale blue during the day but a deep purple color at night. It also glows with a bright orange-red flare in ultraviolet light.
Hackmanite is a rare mineral that isn’t seen much since it is mostly too soft to be worked for jewelry without shattering.
Hematite is an interesting material, and while many people may incorrectly define it as a crystal due to its smooth appearance and mirror-like surface (and the fact that it is often carved into crystalline structures), this stone is a mineral.
Hematite is a form of iron oxide and has the unique property of being magnetic, which makes it a popular healing stone in metaphysical circles.
There are hundreds of precious and semiprecious stones of every color and quality you can think of, so if you’re trying to aim your rockhound collection in a certain direction, try picking a certain color of stones and start searching from there.
TIP: Fluorite is one of the most widespread minerals in crystal collections, most probably the second after quartz. Find out the main differences between real and fake fluorite in the article below:
Real vs. Fake Fluorite: Focus on These 5 Differences
Special Forms of Rocks
Many rockhounds focus their collections on shiny crystals and gemstones, but many kinds of specialized rocks can also add interest and personality to your set.
Here are some special rocks you might consider adding to your collection of rocks and minerals:
Geodes are crystal caves that are formed from bubbles in volcanic rock or burrows, mud balls, or tree roots in sedimentary rock.
Over time, the organic aspects of these caves rot away, leaving a hollow in the sedimentary rock that becomes crystallized. Geodes are often displayed either sliced in half to display the crystal hollow inside or sliced and polished to make them translucent.
- Petrified wood:
Petrified wood is a type of fossil and occurs when vegetation such as a tree trunk becomes mineralized, often taking on the appearance of a crystalline structure.
Unlike some special rock formations, petrified wood is not that rare. It is found in most locations where volcanic activity has occurred at some point in geological history.
Amber is a tree sap that has become mineralized for hundreds of years and is often used as a semiprecious stone in jewelry. Amber is most famous for capturing prehistoric insects and other creatures inside of it, effectively freezing them in time.
Amber that contains organic material such as an insect is typically much more expensive than plain amber, and it can come in several varying shades from a light golden color to almost red coloration.
Fossils occur when organic material becomes trapped in rock matter and decomposes, either leaving a hollow (and a perfect imprint) or petrified bone in its place.
The fossil record is the only reason that humanity currently knows that dinosaurs ever existed. There are many small fossils of everything from prehistoric shark teeth to trilobites that are popular among rockhounds.
Some of these unique rock formations form the focal points for many a rock and gem collection. So if you’re looking to branch out into some minerals other than pure crystals, these are the way to go.
TIP: Do you know which gemstones come from the ocean? I wrote about the most common gemstones from the ocean in this article:
Which Gemstones Come From The Ocean? Corals, Pearls & more!
What Does the Difference Between Rocks, Minerals, and Crystals Mean for Rockhounds?
These three terms refer to somewhat different aspects of the gem and mineral collecting hobby, but the difference between them doesn’t mean much if you’re collecting gems and minerals just to collect them.
It’s a lot more important to pay attention to the differences between different kinds of minerals rather than the difference between their classifications.
Knowing that fluorite isn’t rock is good, but it’s not going to help you grade a piece of fluorite you’re interested in buying or teach you anything about the properties of the mineral.
Instead, rockhounds should focus on learning the properties and lore surrounding each type of mineral and crystal. This is a much more effective use of time for collectors.
Why Are Crystals and Minerals Important?
Even if you don’t believe in the metaphysical properties of crystals, crystals and minerals are a vital part of modern industry.
The unique properties that these inorganic materials possess often make them superior materials for the construction of electronics and tools.
Minerals are also an important part of the makeup of biological creatures. Without exposure to the right combination of minerals, living things cannot continue to sustain life.
Minerals form some of the most basic building blocks of the human body, along with the cellular structure of every animal and plant across the world.
TIP: Rock tumblers use various types of grit in the multiple stages of the rock tumbling process to shape, smooth, and polish the stones. Find out everything about tumbling grit in the article below:
Rock Tumbling Grit: Usage, Types, Disposal & Substitutes
Tips for Learning the Differences Between Minerals and Crystals
When you’re gathering up a collection of rocks and minerals, it can be difficult to keep them all straight after a certain amount of time or after you’ve amassed a large enough collection.
Sometimes it can be difficult to tell the difference between certain minerals and crystals that look very similar in coloration or shape.
Here are some tips for figuring out the differences between the rocks, minerals, and crystals that you collect:
- Keep everything labeled.
The easiest way to keep your collection organized is to put it into a clear container like one designed to separate craft beads. Each compartment of the container can be labeled so that you know every crystal and where it’s supposed to go.
- Catalog your finds.
This is especially important if collecting rocks and gems in the field is a part of your hobby, as you may need to consult with geographical notes to determine what type of rock or mineral you’ve found.
- Join a gemology or rockhound club.
Not only is it more fun to share the hobby of collecting minerals with other people that share your passion, but you’re also much more likely to find good rocks and minerals on collection field trips if you go with more experienced rockhounds who know exactly where to look.
- Make flashcards.
It might seem like something out of grade school, but flashcards are a great way to teach yourself the basic physical qualities of different minerals and make you better at being able to identify them on sight.
If you’re interested in the alleged metaphysical properties of rocks and crystals, these kinds of notes can also be memorized via flashcards.
- Keep the label your specimens came with.
These labels are especially important for more obscure specimens in case you need to look something up about them and can’t remember the spelling of the name.
Many labels also denote the history of the specimen, and it’s these kinds of details that make each rock and gem specimen unique.
- Limit your collection.
It may be fun just to purchase any rock or gem that catches your eye, but more impressive collections usually go along with some kind of theme, like a collection of fossils from a certain period of history or crystals according to their metaphysical properties.
If you display them well, you’re always free to collect as many minerals as you like, but limiting your collection to a few high-quality pieces can be easier to display and more valuable.
- Check out a rock and gem expo.
These large events often have dozens of vendors available where you can find unique specimens of some of the rarest minerals and rocks in the world.
Depending on where you live, you might have to do a bit of traveling to attend, but the chance to buy unique specimens is definitely worth the trip.
- Make connections in the rockhound world.
Often in rock and mineral collecting, it’s as much about who you know as it is about what you know. Getting linked up with more experienced gemologists can not only expose you to markets with high-quality minerals you wouldn’t otherwise be aware of, but it can also give you some socialization.
You can work on your collection at your leisure, so don’t feel pressured to spend hundreds of dollars to purchase specimens right off the bat.
Build your collection slowly and only acquire pieces that have special meaning to you. The more organized and well-displayed your collection is, the more pride you’ll end up taking in it.
Learning the Real Difference Between Minerals Takes a Lifetime of Study
Knowing the basic differences between a rock, a mineral, and a crystal are just the first step to becoming a rockhound.
The real bulk of the knowledge you need to know to collect gems, rocks, and minerals are to learn the difference between the specific types of minerals and rocks you’re collecting.
Luckily, there are so many around the planet that you could collect minerals and crystals for the rest of your life and probably never run out.
So, take your time and learn about what makes rocks, minerals, and crystals unique so that you can build a fantastic collection that you’ll be proud to show off!
TIP: Rock collecting can mean anything between picking up the odd rock on a hike and keeping a full mineral display shelf at home. Check out the complete guide on how to start rock collecting in the article below:
How to Start Rock Collecting? Complete Guide for Beginners