With so many crystals available online, it can sometimes be difficult to know exactly what you are buying.
Some crystals are completely natural, while others may have been heated, dyed, coated or otherwise treated to change their appearance. There are also genuine minerals that are sold under misleading names, along with glass and other man-made materials that can look remarkably similar to natural crystals.
So how can you tell the difference?
After more than 25 years of working with crystals and minerals, I have found that the most useful approach is not to rely on one simple test. Instead, look at the whole specimen — its colour, structure, weight, inclusions, crystal formation and, most importantly, its provenance.
Here are some simple things you can look for.
1. Look at the Way the Crystal Has Formed
One of the first things I look at is the structure of the specimen.
Natural crystals grow over time, often producing distinctive crystal faces, growth patterns, fractures and inclusions. These can vary considerably, even between pieces from the same locality.
A natural Quartz crystal, for example, may contain internal veils, fractures, mineral inclusions or areas of different transparency. These features are part of its geological history.
This doesn't mean that a perfect-looking crystal is automatically fake. Some natural crystals can be remarkably clear and well formed. Likewise, an unusual inclusion or perfectly formed crystal face is not, on its own, proof of authenticity.
It is the overall appearance that matters.
2. Look Carefully at the Colour
Colour can tell you a great deal about a specimen.
Natural minerals often show subtle variations in colour and transparency. Some have zoning, patches of different colours or gradual transitions between shades.
Strong, unnaturally bright colours can sometimes indicate dyeing or another treatment, particularly when the colour appears concentrated around cracks, holes or the surface of a stone.
Dyed Agate is a good example. The Agate itself is genuine, but its colour may have been artificially enhanced.
This is an important distinction: a treated crystal isn't necessarily a fake crystal.
A mineral can be completely genuine while having been heated, dyed or otherwise treated.
3. Be Careful With the Scratch Test
You will often see the advice to scratch a crystal against glass to determine whether it is genuine.
There is some useful science behind this, but I don't recommend using it as your first test.
The Mohs scale measures a mineral's resistance to scratching. Quartz has a hardness of 7, while ordinary glass is generally around 5–6. Quartz can therefore scratch glass.
However, scratching your specimen can damage it, and the test doesn't prove that a specimen is natural. Synthetic Quartz, for example, is still Quartz and has the same hardness.
A scratch test can therefore provide information about hardness, but it cannot tell you the complete story of where a specimen came from.
4. Don't Rely Too Heavily on the Temperature Test
You may have heard that a real crystal will feel cold when you first pick it up, whereas glass or plastic will feel warmer.
There is some truth behind the observation, but it is not a reliable way to identify a mineral.
Different materials conduct heat differently, and the temperature of the room, the size of the specimen and how you have been holding it will all affect how it feels.
A Quartz crystal may feel noticeably cool when you first pick it up, but this doesn't prove that it is natural Quartz.
I would therefore treat the temperature test as an interesting observation rather than an authenticity test.
5. Examine Bubbles and Inclusions
This can be particularly useful when trying to distinguish glass from a natural mineral.
Under magnification, manufactured glass can sometimes contain perfectly rounded air bubbles. Natural minerals can also contain fluid inclusions and other internal features, but these often have very different shapes and characteristics.
Don't assume that every bubble means glass, though.
Some natural minerals contain fluid inclusions, gas bubbles or other fascinating internal structures. In some specimens, these inclusions are actually one of the features that makes the mineral particularly desirable to collectors.
A loupe or microscope can reveal an enormous amount about a specimen.
What About the Weight?
Weight can sometimes provide another clue, but again, it isn't proof of authenticity.
Different minerals have different densities, so two specimens of exactly the same size can have noticeably different weights.
Plastic may feel unusually light, while glass can sometimes feel surprisingly substantial. However, many natural minerals are also relatively light, and some man-made materials can have a density very similar to natural stone.
If you know what mineral you are looking at, comparing its size and weight with its expected density can be useful.
For a serious identification, however, there are much more reliable methods than simply holding a stone in your hand.
Three Common Examples That Cause Confusion
Amethyst Sold as Citrine
This is probably one of the most common areas of confusion.
Natural Citrine does occur, but much of the material sold commercially as Citrine is actually Amethyst that has been heat treated.
Heat-treated Amethyst can develop yellow, orange and brown colours, sometimes producing the dramatic burnt-orange appearance often seen in crystal shops and online marketplaces.
The material is still genuine Quartz and the Amethyst is genuine — it has simply been altered by heat.
This is why I think it is more accurate to describe it as heat-treated Amethyst rather than simply calling it fake Citrine.
Natural Citrine tends to have a different appearance and is considerably less common.
Dyed Howlite Sold as Turquoise
Howlite is a genuine mineral and can be attractive in its own right. Because it is usually white or pale in colour, it can be dyed blue and sold as an imitation of Turquoise.
With experience, there are often clues.
Dyed material may show stronger colour around cracks or holes, while natural Turquoise has its own distinctive mineral structure and appearance.
Again, the important point is that the Howlite itself isn't fake. It is the description that can be misleading.
Opalite and Goldstone
These are slightly different examples because they are not natural minerals in the first place.
Opalite is a man-made glass material, while Goldstone is also manufactured glass containing tiny metallic particles that produce its characteristic sparkle.
Both can be attractive materials, and there is nothing wrong with buying them if you like them.
The important thing is simply to know what you are buying.
For a mineral collector looking for natural specimens, Opalite and Goldstone belong in a different category from naturally occurring minerals.
So, How Can You Be Certain?
The simple answer is that there isn't one test that can identify every crystal.
Experienced collectors develop an eye for minerals by handling thousands of specimens and learning how different minerals form. Locality is also extremely important. Knowing where a specimen came from can tell you whether its appearance is consistent with material known from that locality.
For more difficult specimens, professional mineral identification can involve techniques such as specific gravity, refractive index, hardness testing, microscopy, spectroscopy or chemical analysis.
You don't need to carry a laboratory around with you to enjoy collecting crystals, though.
Start by looking carefully.
Ask yourself:
- Does the specimen look like the mineral it is being sold as?
- Does its crystal structure make sense?
- Are the colour and inclusions natural-looking?
- Has the specimen been treated or enhanced?
- Is the description clear about any treatment?
- Where did the specimen come from?
- Is the seller knowledgeable about the material?
These questions will take you much further than simply performing a scratch or temperature test.
A Note From Me
After more than 25 years of working with crystals and minerals, I still find that one of the most enjoyable parts of collecting is learning to look more closely.
Every specimen has a story.
Its crystal shape, inclusions, colour and locality can tell us something about the conditions in which it formed and the journey it has taken since leaving the ground.
That is one of the reasons I am careful about how I describe the crystals I offer through KSC Crystals. I want you to know what you are buying, including when a mineral has been treated or enhanced.
I was also entrusted with the care of a significant part of Judy Hall's personal crystal collection, which has given me the opportunity to handle many of the specimens that featured in her books.
You can read more about that journey in A Keeper's Tale.
Buying Crystals With Confidence
You don't need to become a mineralogist to start collecting crystals.
The more specimens you handle, the more familiar you become with the natural variations found within different minerals. Over time, you begin to notice things that photographs often don't show.
My advice is simple: look beyond the colour and the name.
Learn about the mineral, its locality and the way it naturally forms.
And if you are unsure about a specimen, ask questions before you buy it.
A good mineral dealer should be happy to tell you what they know about a specimen and, where appropriate, whether it has been treated or enhanced.
That is how you build a collection you can enjoy with confidence — not because every crystal is perfect, but because you understand what you have bought.
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