Ruby: A Buying and Care Guide From Our Bench
A customer brought in a ruby ring last winter that her mother had worn for thirty years. Good red, oval stone, a little over two carats, set in yellow gold. She wanted it cleaned and the prongs checked. Under the microscope the stone showed a network of flash-coloured seams running through the cracks, which is what lead glass looks like when light hits it at the right angle. It was a fracture-filled ruby. Her mother had loved it, worn it every day, and nobody had ever told her it could not go in an ultrasonic cleaner. It had survived on luck. That is the single most useful thing to know before you buy a ruby, so we are putting it near the top.
Ruby and sapphire are the same mineral
This is the fact that stops people mid-sentence at our counter. GIA puts it directly: ruby is one variety of the corundum mineral species, which also includes sapphire.
Corundum is aluminium oxide. On its own it is colourless. When it grows with a trace of chromium inside it, it comes out red, and we call it ruby. When it grows with traces of iron and titanium instead, it comes out blue, and we call it sapphire. Yellow, green, orange, violet and pink corundum all exist too, and every one of them is called a sapphire. Red is the only colour that gets its own name.
So a ruby and a blue sapphire have the same hardness, the same toughness, the same cleavage behaviour and the same care requirements. If you have read our piece on why sapphire engagement rings are making a comeback, everything in it about durability applies here word for word.
Chromium does two jobs
Chromium is what makes a ruby red. GIA explains that the strength of ruby's red depends on how much chromium is present, and the more chromium, the stronger the red colour.
Its second job is less obvious and it is worth knowing about, because it changes how a stone behaves outside the shop. Chromium makes many rubies fluoresce, which means they give off a red glow when ultraviolet light falls on them. There is ultraviolet in ordinary daylight. GIA notes that fluorescence can make a ruby's colour even more intense and increase its value.
This is why a good ruby can look as though a light has been switched on inside it when you step outside with it, and why the same stone can look heavier and darker under a shop's warm lamps. Take any ruby you are considering to a window before you decide.
Iron works against the red
Where a ruby formed in the ground changes what it looks like. GIA describes the most renowned rubies, including those from Myanmar, the Himalayas and northern Vietnam, as forming in marble, and explains that marble has low iron content, so the rubies that originate in marble lack iron, and because of this many have an intense red colour.
Rubies that formed in basalt, a volcanic rock, tend to carry more iron. GIA states that rubies from these sources can have higher iron content, which can make the rubies darker and less intense in colour. Iron also damps down the fluorescence, so those stones lose the daylight glow as well as some of the brightness.
You do not need to memorise deposit types to buy well. Just understand that origin is a real driver of appearance and price in the ruby trade, and that a seller quoting an origin on an expensive stone should be able to back it with a lab report.
The colour line that moves the price
Here is where ruby buying gets genuinely difficult. Red corundum does not arrive in two neat buckets. The colour runs continuously from the palest pink through to deep red, and somewhere along that run the trade stops calling a stone a pink sapphire and starts calling it a ruby.
That point is a judgement call. Labs have their own standards, markets in different countries draw it in different places, and two competent graders can look at the same stone and reach different conclusions. The stone does not change. The name on the paperwork does, and the price follows the name by a wide margin.
Our advice is simple. Buy the colour you like, at a price that makes sense for the stone in front of you, and treat the word on the certificate as one input rather than the verdict. A pink sapphire you love at a price you can afford beats a borderline ruby bought for the label. If the colour matters to you as much as the name, the wider field of options is worth reading: we covered it in our guide to coloured gemstone engagement rings.
What top colour actually looks like
GIA describes the finest ruby as a pure red through to a red with a purplish cast, and says that rubies with overtones of orange and purple are less valued.
Three things move together and you should judge all three at once.
Hue is the basic colour. Pure red is the target. A red pulled toward orange reads warm and brick-like. A red pulled far toward purple reads like a raspberry.
Saturation is how strong the colour is. Weak saturation reads pink. Strong saturation is what gives a ruby its presence.
Tone is how light or dark the stone is. Too light and the red washes out. Too dark and the stone goes black in the corners of the room and stops returning light. The stones that hold their colour in a dim restaurant are the ones people fall in love with.
Inclusions: the rules are different from diamonds
If you bring diamond habits to a ruby you will reject good stones for no reason. GIA states that inclusion-free rubies are practically nonexistent.
An inclusion is anything trapped inside the stone as it grew. In ruby that might be a small crystal of another mineral, a healed crack that looks like a fingerprint, or a field of fine needles. The trade expects them. What GIA warns about is the ones you can see and the ones that dull the stone: obvious inclusions, or inclusions that reduce transparency or brightness, lower a ruby's value dramatically.
The inclusion that helps
Rutile silk is a mesh of very fine needles of the mineral rutile. In modest amounts it does something useful. GIA explains that it causes light to scatter across facets that might otherwise be too dark, adds softness to the colour, and spreads the colour more evenly across the ruby's crown.
Put plainly: silk catches light that would otherwise fall into the dark parts of the stone and throws it back out, so the red reads evenly across the whole face instead of pooling. Too much of it turns the stone hazy and takes value away. The right amount makes a ruby glow.
So when we say a ruby's inclusions are acceptable, we are making a judgement about position, visibility and effect. That is a different skill from grading a diamond, and it is why we ask customers to look at the stone rather than the paperwork first.
Treatments: where buyers get hurt
Nearly every ruby on the market has been treated in some way. The treatments are not equal, and the difference between two of them is the difference between a stone that will outlive you and a stone you have to protect from lemon juice.
| Treatment | What is done | Safe cleaning | What to expect on price |
|---|---|---|---|
| None | Cut and polished, nothing else | Warm soapy water; ultrasonic and steam usually safe | Highest. Needs a lab report to command it. |
| Heat | High temperature improves colour and dissolves some silk | Warm soapy water; ultrasonic and steam usually safe | Standard across the trade. Accepted when disclosed. |
| Lattice diffusion | Elements driven into the stone at high heat to alter colour | Warm soapy water; ultrasonic and steam usually safe | Below heated stones. Must be disclosed. |
| Fracture filling with lead glass | Cracks filled with high-lead-content glass to hide them | Damp cloth only | A fraction of a comparable heated ruby. A different product. |
| Cavity filling | Surface pits filled to smooth the stone | Damp cloth only | Low. Must be disclosed. |
| Dyeing | Colourant added, usually into fractures | Damp cloth only | Lowest. Colour can fade or leach. |
Heat is fine. Say so in writing.
Heating ruby is old, stable and permanent, and the trade has accepted it for decades on one condition: the seller tells you. GIA groups heat-treated stones with untreated ones for cleaning purposes, noting that ultrasonic and steam cleaners are usually safe for untreated, heat-treated, and lattice diffusion treated stones. A heated ruby is a real ruby with a normal life ahead of it.
Lead glass filling is a separate product
Start with what gets filled. The rough is low-grade corundum so full of cracks that it has no use as a gem. Molten high-lead-content glass is drawn into those cracks, where it bends light in a similar way to the stone, so the fractures stop showing. What comes out is a large red stone at a small price.
GIA describes these stones as having surface-reaching fractures filled primarily with a high-lead content glass, and says that even relatively mild substances like lemon juice can cause changes in the high-lead content glass. GIA is direct about the consequence too: this material requires special care and should only be cleaned with a damp cloth.
Read that list again through the eyes of someone living a normal life. Lemon juice is in salad dressing. Vinegar is in most household cleaners. A jeweller's ultrasonic tank and a steam cleaner are the standard tools for a free cleaning at any shop counter, including ours. A filled ruby handed across a counter without disclosure can come back cloudy, and the customer will never know why.
We have no objection to selling a filled stone to somebody who wants a big red ring for a small budget and knows what they are getting. What we object to is the same stone sold at a fine ruby price with the word treated doing all the work.
The two questions to ask, every time
Ask them out loud, in this order, of any ruby at any price.
- Is this ruby heat treated? The answer will almost always be yes.
- Is this ruby fracture filled or glass filled? This is the answer that changes the price and the care for the rest of the stone's life.
Then ask for both answers written on the receipt. A seller who is confident in the stone will write it without hesitation. Hesitation is your answer.
On anything above a couple of thousand dollars, ask for an independent lab report as well. GIA and other major labs identify fracture filling routinely, and the cost of the report is small against the cost of being wrong.
Size, cut and why fine rubies get expensive fast
GIA notes that fine-quality rubies over one carat are very rare, and that the price per carat goes up significantly for ruby as it increases in size.
That second point catches people out. Price per carat rising with size means a two carat fine ruby costs more than twice a one carat fine ruby of the same quality, sometimes far more. The stone got twice as heavy and the price did something steeper.
On cut, GIA reports that the most common shapes of fashioned rubies are ovals and cushions. There is a practical reason behind that. Ruby rough often grows in a flat, tabular shape, and cutters choose the outline that saves the most weight from that shape while keeping the colour looking its best. Cutting a coloured stone is a colour decision first and a sparkle decision second, which is the reverse of how a diamond is cut.
Ruby as an everyday ring stone
This is where ruby earns its place. GIA lists ruby at 9 on the Mohs hardness scale, with excellent toughness and no cleavage.
Two separate properties are doing the work there. Hardness is resistance to scratching, and at 9 only diamond and a few synthetic materials will scratch a ruby. Toughness is resistance to chipping and breaking when the stone takes a knock. Cleavage is a built-in plane of weakness that some minerals split along. Ruby has none.
Compare that with emerald, which sits lower on both counts and carries fractures as a matter of course. We wrote about that trade-off in whether emeralds are durable enough for an engagement ring. Ruby is in another class. Among coloured stones, ruby and sapphire are the two we recommend without reservation for a ring worn every day, and our wider comparison of jewellery care by gemstone hardness sets out where each stone lands.
The durability argument holds for untreated, heated and lattice diffusion treated stones. A lead-glass-filled ruby is as hard as any other corundum, and the glass in its cracks is the weak point, so it belongs on a different list.
How to clean a ruby at home
For an untreated or heat-treated ruby, GIA says warm soapy water is always safe. That is our whole method. Warm water, a drop of dish soap, a soft toothbrush worked around the back of the setting where the film builds up, then a rinse and a lint-free cloth. Do it over a bowl rather than an open drain.
If the stone is fracture filled, cavity filled or dyed, use a damp cloth and nothing else, per GIA. Keep it away from ultrasonic tanks, steam, acids and household cleaners, and take it off before you cook or clean.
Bring it to us once a year either way and we will check the prongs under magnification. Hardness 9 protects the stone. It does nothing for the gold holding it in.
Rings in our cases
Pieces you can try on in Coquitlam, and a starting point if you are thinking about a ruby of your own.
Key Takeaways
- Ruby and sapphire are the same mineral. GIA states ruby is one variety of the corundum species, which also includes sapphire; red corundum is ruby and every other colour is sapphire.
- Chromium causes the red and also makes many rubies fluoresce, which GIA says can make the colour more intense and increase value. Look at any ruby in daylight before deciding.
- Perfect rubies do not exist. GIA states inclusion-free rubies are practically nonexistent, and rutile silk in modest amounts scatters light across facets that would otherwise be too dark.
- Heat treatment is standard and accepted when disclosed. Lead-glass fracture filling is a separate product that GIA says should be cleaned with a damp cloth only, because even lemon juice can change the high-lead glass.
- Ask two questions and get both answers in writing: is it heat treated, and is it fracture filled. On an expensive stone, ask for an independent lab report as well.
Frequently Asked Questions
What is the difference between a ruby and a sapphire?
They are the same mineral. GIA states that ruby is one variety of the corundum mineral species, which also includes sapphire. Red corundum gets called ruby. Corundum in any other colour gets called sapphire, which is why blue sapphire, yellow sapphire, green sapphire and pink sapphire all exist and none of them are called ruby. This surprises almost everyone who hears it at our counter, because the two stones sit at different prices and carry different reputations. The chemistry is identical: aluminium oxide, hardness 9, no cleavage. What separates them is a trace of another element that sneaked into the crystal while it grew. Change the trace element and you change the name, the price and the whole conversation about the stone.
What makes a ruby red?
Chromium. GIA explains that the strength of ruby's red depends on how much chromium is present, and the more chromium, the stronger the red colour. Pure corundum with nothing else in it is colourless. A few chromium atoms sitting in the crystal structure absorb part of the light passing through and let the red through. Chromium does a second job as well. It makes many rubies fluoresce, meaning they give off a red glow under ultraviolet light, including the ultraviolet in ordinary daylight. GIA notes that fluorescence can make a ruby's colour even more intense and increase its value. That is part of why some rubies look as if they are lit from the inside when you step outdoors with one.
Where is the line between a ruby and a pink sapphire?
There is no line written into the stone, and that is the honest answer. The colour runs in a continuous band from pale pink through to deep red, and somewhere in that band a stone stops being called a pink sapphire and starts being called a ruby. Where exactly is a judgement call, and different labs and different markets draw it in different places. The commercial effect is real, because the name changes the price by a wide margin on the same piece of corundum. Our advice is to buy the colour rather than the word. Look at the stone in daylight, look at it under a lamp, decide whether you like what you see, and treat the label on the paperwork as one more piece of information. If a seller leans hard on the word ruby for a stone that reads pink to your eye, ask which lab graded it and ask to see the report.
What colour should I look for in a ruby?
GIA describes the finest ruby as a pure red through to a red with a purplish cast, and says that rubies with overtones of orange and purple are less valued. An overtone is a second colour you can see sitting on top of the main red, the way a tomato red and a brick red differ. Depth of colour matters as much as hue. A stone that is too pale reads pink, and a stone that is too dark loses its glow and goes flat under low light. The colour you want is saturated enough to be obviously red across the room and still bright when you carry it into a dim restaurant. Look at any ruby under at least two light sources before you buy it, because many coloured stones look wonderful under a jewellery case spotlight and dull at a kitchen table.
Do rubies have inclusions, and are they a problem?
Every ruby has them. GIA states plainly that inclusion-free rubies are practically nonexistent, and the trade expects to see at least some. An inclusion is anything trapped inside the stone while it grew: a tiny crystal, a fingerprint-shaped pattern, or fine needles. So the question is never whether a ruby has inclusions. It is which ones and where. GIA notes that obvious inclusions, or inclusions that reduce transparency or brightness, lower a ruby's value dramatically. Something sitting under the table of the stone where the eye lands first costs you more value than the same thing tucked near the girdle. If you come in with a loupe expecting a clean ruby, we will gently talk you out of it, because that expectation belongs to diamonds.
What is rutile silk and does it help or hurt?
Rutile silk is a mesh of extremely fine needles of the mineral rutile, grown inside the ruby, that looks like a faint silky sheen when light hits it. It is one of the few inclusions that can work in your favour. GIA explains that silk causes light to scatter across facets that might otherwise be too dark, adds softness to the colour, and spreads the colour more evenly across the ruby's crown. In plain terms, a modest amount of silk fills in the dead spots and makes the red read evenly across the whole face of the stone. Too much silk goes the other way and turns the ruby cloudy, which costs value. Heat treatment is often used to dissolve some of the silk and open the stone up, and that is a legitimate, disclosed practice. Silk is worth understanding before you dismiss a stone for not being clean.
Is heat treatment acceptable in a ruby?
Yes, and it is standard. Heating ruby to high temperatures improves colour and can dissolve some of the silk that makes a stone look cloudy. It is stable, it is permanent, and the trade has accepted it for decades on the condition that the seller tells you. Treat it as a normal part of the coloured stone market rather than something being hidden from you. GIA's own care guidance puts heat-treated ruby in the same bracket as untreated ruby for cleaning, noting that ultrasonic and steam cleaners are usually safe for untreated, heat-treated, and lattice diffusion treated stones. What matters is disclosure. Ask the seller directly whether the ruby is heated, and ask for the answer in writing on the receipt. A seller who cannot or will not answer that question is telling you something.
What is a lead-glass filled ruby and should I buy one?
It is a different product from a fine ruby, sold at a different price, and it needs different care. Low-grade, heavily fractured corundum is soaked with molten high-lead-content glass that seeps into the cracks. The glass has a similar sparkle to the stone, so the fractures stop showing and a piece of rough that was unsellable becomes a large red stone at a low price. GIA describes these as having surface-reaching fractures filled primarily with a high-lead content glass, and warns that even relatively mild substances like lemon juice can cause changes in the high-lead content glass. Buy one with your eyes open if you want a big red stone for a small budget. Ask the price to reflect what it is, ask for it in writing, and expect to be careful with it for the rest of its life.
How do I clean a ruby ring at home?
For an untreated or heat-treated ruby, warm water with a drop of dish soap and a soft toothbrush around the setting. GIA says warm soapy water is always safe, and that ultrasonic and steam cleaners are usually safe for untreated, heat-treated, and lattice diffusion treated stones. Rinse, dry with a lint-free cloth, and check the prongs while it is clean. If your ruby is fracture filled, cavity filled or dyed, the rules change completely. GIA states that fracture-filled, cavity-filled, or dyed material should only be cleaned with a damp cloth. No ultrasonic, no steam, no soaking, and keep it away from lemon juice, vinegar and household cleaners. If you do not know which kind you own, treat it as filled until somebody tells you otherwise.
Sources
- GIA: Ruby Description (corundum species, chromium, marble and basalt sources, fluorescence)
- GIA: Ruby Quality Factors (colour, inclusions, rutile silk, cut, carat weight)
- GIA: Ruby Care and Cleaning Guide (Mohs 9, toughness, cleaning by treatment type)
Data sourced September 2026. All hardness, colour, inclusion, treatment and cleaning points are GIA's. The pricing comments, the two questions to ask a seller, and everything we describe seeing at the counter are our own view and our own experience at the bench in Coquitlam.
Visit Vanhess
We are a family-run studio at 2929 Barnet Highway in Coquitlam, and we designed and made most of what sits in our cases. Bring a ruby in and we will look at it under magnification with you, tell you what we can see about how it was treated, and say plainly when a stone needs a lab report rather than our opinion. We will also check the prongs while you wait. Call us at +1 (604) 653-6449.
