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Minerals · Cristalljoia Barcelona
Emerald, ruby and sapphire: why raw minerals are so cheap compared to jewellery
When someone sees emeralds, rubies or sapphires in rough form in our shop priced at just a few euros, the most common reaction is surprise. "But aren't those incredibly expensive?" The answer is yes and no, depending on exactly what we're talking about. These three gems are, along with diamond, what are known as the classic precious stones. Their names carry enormous weight in the collective imagination. But the mineral and the jewellery-grade stone are two very different things, even if they are chemically identical.
What they actually are
Ruby and sapphire are the same mineral: corundum, an aluminium oxide (Al₂O₃). The only difference between them is the trace element that gives each its colour: chromium produces ruby's red, while titanium combined with iron produces sapphire's blue. Any corundum that is not red is called a sapphire, even if it is yellow, green, orange or pink.
Emerald, on the other hand, is a variety of beryl, an aluminium beryllium silicate. The characteristic green colour comes from chromium and, in some cases, vanadium. Beryl produces several other well-known varieties: aquamarine is blue beryl, morganite is pink beryl, heliodor is yellow beryl. Same mineral family, different colour depending on which trace elements were present during formation.
Mineralogy in one line
- Ruby: red corundum (chromium)
- Sapphire: corundum of any other colour (titanium, iron, or others)
- Emerald: green beryl (chromium, vanadium)
Why the same mineral can be worth cents or thousands of euros
The name does not determine the price. What determines it is crystal quality. In nature, corundum and beryl form under very specific geological conditions: high temperatures, particular pressures, and the presence of the right elements at exactly the right moment. When all those conditions align perfectly, the mineral forms transparent, well-defined crystals with a saturated, uniform colour. When they don't, the result is a mineral with the same chemistry but without the optical qualities that give it value as a gem.
Of all the corundum and beryl extracted in the world, only a tiny fraction has gem quality. The vast majority is opaque, granular or has too many internal inclusions. That material exists in far greater quantities than high-quality gems, and its price reflects exactly that.
What turns a mineral into an expensive gem
- Transparency: the crystal must allow light to pass through clearly.
- Saturated, uniform colour: intense and pure, with no dull or uneven areas.
- Few visible inclusions: the fewer internal impurities, the greater the value.
- Size: large, clean crystals are statistically extremely rare.
What "uncrystallised" mineral means
When we talk about uncrystallised emerald, ruby or sapphire, we mean specimens in which the mineral has not formed defined or transparent crystals. Instead of a well-formed crystal, what we have is a compact, granular or earthy-looking mineral mass. The colour may be intense and recognisable, the chemical composition is exactly the same, but the transparency and crystalline structure that jewellery demands are simply not there. It is the genuine mineral, in a different state.
At Cristalljoia we carry emerald, ruby and sapphire in rough and uncrystallised form: interesting pieces for collecting, for getting to know the mineral in its natural state, or simply for having a genuine emerald at home at a very accessible price.
Curiosities
Corundum sands metal
With a hardness of 9 on the Mohs scale, low-quality corundum is used as an industrial abrasive: sandpaper, grinding wheels, cutting discs. The same mineral that in perfect form is a ruby, in its common form helps sand steel.
Sapphire can show a star
Some sapphires display a six-rayed star on their surface when cut into a cabochon. These are called star sapphires, and the effect is caused by microscopic inclusions of rutile oriented in three directions.
Emerald inclusions have their own name
In emeralds they are so common that the trade calls them jardin (French for garden), because under a loupe they resemble a leafy landscape. A completely clean emerald is so rare that its very clarity raises suspicion.
The British Crown's "Ruby" is not a ruby
The famous Black Prince's Ruby, set in the British Imperial Crown, is actually a red spinel — a completely different mineral. Until the 19th century the two could not be reliably distinguished, and many historical gems carry incorrect names.
Beryl can measure metres
Beryl crystals several metres long and weighing hundreds of kilos have been found. They are opaque and have no value as gems, but are spectacular as mineral specimens. Gem-quality emerald crystals rarely exceed a few centimetres.
Sapphire comes in every colour
Yellow, green, orange, pink, violet, colourless… any corundum that is not red is a sapphire. The Padparadscha, with its pink-orange tone, is one of the rarest and most valuable. Blue is the best known, but far from the only one.
Key takeaways
- Ruby and sapphire are the same mineral with different colour-causing traces.
- Emerald is green beryl, just as aquamarine is blue beryl.
- The vast majority of corundum and beryl extracted worldwide does not have gem quality.
- Price depends on crystal quality, not on the mineral's name.
- Raw mineral is genuine: same chemistry, without the optical qualities of jewellery.
Looking for a specific mineral?
At our physical store in the centre of Barcelona we have many more options than what you see online.
If you can't find what you're looking for online, message me on WhatsApp at +34 670 61 16 63.
I'm Jéssica and I'll be happy to help.
