If you read our sapphire guide, you already know the punchline: ruby and sapphire are the same mineral. Corundum that grew with chromium in it comes out red and gets called ruby. Corundum that grew with anything else comes out blue, pink, yellow, or colorless and gets called sapphire. One trace element, two names, and an enormous difference in price, because fine red corundum is far scarcer than fine blue. At the very top of the market, ruby is the most expensive colored gemstone on earth by weight. This guide covers how to judge ruby color, why some rubies seem to glow, the treatment every buyer needs to understand, and how to choose a piece when there is only one of it.
What ruby is, and where the line sits
Ruby is red corundum, colored by traces of chromium. That same chromium is what makes emerald green in a different mineral, and it is a demanding element to work with: it produces glorious color, but it also tends to leave the crystal strained and included. This is why large, clean rubies are so much rarer than large, clean sapphires.
There is a genuine gray area worth knowing about. Chromium in smaller amounts produces pink rather than red, and there is no universal scientific line where pink sapphire ends and ruby begins. Different markets draw it in different places, with the American trade generally requiring a stronger, more saturated red before calling a stone ruby. This is not a trick, it is an honest ambiguity in the middle of a color scale, and it is the reason two stones that look similar can carry different names and very different prices.
Judging the color
With ruby, color is the overwhelming driver of value, and the vocabulary around it is old and loaded.
The term you will hear is pigeon's blood, traditionally used for the finest Burmese material: a pure, vivid red with a faint blue undertone rather than an orange one, and no darkness dulling it. Several gem laboratories now issue it as a formal color grade rather than leaving it as poetry. Treat the phrase with some care when a seller uses it casually, because without a laboratory report behind it, it is a description, not a certification.
What you are actually looking for is a red that is strongly saturated and sits in a medium to medium-dark tone. Too dark and the stone reads garnet-like and lifeless. Too light and you are in pink sapphire territory. An orange or brownish cast lowers value, while a whisper of blue or purple in the red raises it.
Why some rubies glow
Here is the property that separates a merely red ruby from a memorable one. Chromium does not only color the stone, it makes it fluoresce red under ultraviolet light, and daylight contains plenty of ultraviolet. A ruby with strong fluorescence appears to light up from inside, as though the color has its own power source.
Iron suppresses this effect. Rubies from low-iron deposits, classically Burma, tend to glow. Material from higher-iron sources reads darker and flatter by comparison. This is why two rubies with similar color on paper can look entirely different across a dinner table, and it is worth looking for when you compare stones.
Where ruby comes from
The Mogok valley in Myanmar, long known as the Valley of Rubies, is the historic source and still the reference point for the finest material. Mozambique changed the modern market: major deposits found there around 2009 now supply a large share of the world's fine ruby, and the quality is excellent. Thailand has been central to ruby cutting and trading for generations and produces darker, higher-iron stones of its own. Sri Lanka, Madagascar, Vietnam, Tanzania, and Afghanistan all contribute as well.
Every piece we sell states the natural origin of its stones on the accompanying document. It does not name a specific mine, because responsible origin determination is a laboratory question rather than a sales claim.
The impostors, and a famous one
Ruby has been counterfeited, imitated, and honestly mistaken for longer than almost any other gem, and the history is genuinely entertaining.
Red spinel fooled everyone for centuries. It occurs alongside ruby in the same deposits, looks remarkably similar, and was simply called ruby until nineteenth-century mineralogy separated them. Several of the most famous "rubies" in European crown jewels are spinels, including the great red stone in the British Imperial State Crown. Spinel is a lovely gem in its own right, and now that it is correctly identified it is a connoisseur's stone rather than a pretender: see Spinel Jewelry.
Red garnet has played the same role at a lower price point, sold historically under names that borrowed ruby's prestige. Garnet is a beautiful and honest stone when sold as itself, and you can browse it in Garnet Jewelry. The lesson is the same one in both cases: with red stones especially, the identification on the paperwork is the thing that matters.
Treatment, stated plainly
This is the most important section in this guide, because ruby has one treatment that buyers genuinely need to understand.
Heat treatment is routine and unremarkable. Most ruby on the market has been heated to improve color and clarity, the change is permanent and stable, and the practice is accepted throughout the trade. A fine untreated ruby commands a substantial premium precisely because it is uncommon.
Lead-glass filling is the one to know about. Heavily fractured, low-grade corundum can be filled with high-lead-content glass, which fills the cracks, makes them nearly disappear, and turns material that was almost unsaleable into something that looks like a transparent red gemstone. These stones are sometimes called composite rubies. They are inexpensive, they are legal to sell when disclosed, and they are sold in enormous quantities, often to buyers who have no idea what they are holding.
The problem is durability rather than honesty in the abstract. Glass-filled ruby can be damaged by ordinary household acids, including lemon juice. It can be wrecked by an ultrasonic cleaner. It can be destroyed outright by a jeweler's torch during a routine ring repair, which is how many owners find out. A filled stone is not worthless, but it is not the same object as a heated ruby, it must not be cleaned or repaired the same way, and it should never be priced as though it were.
Our position is simple: whatever applies to a specific piece is written on the appraisal that comes with it, including filling if a stone has been filled. We do not hide it in a footnote or leave you to discover it at a repair bench. We explain how to read every line of that document in How to Read a Jewelry Appraisal. Synthetic ruby has also been manufactured since the early 1900s and is extremely common; we sell only natural, earth-mined stones, and our reasoning is in Natural vs Lab-Grown Gemstones.
Is ruby rare?
Yes, and at the top of the market it is the rarest thing we sell. Fine ruby above a few carats, untreated, with strong color and reasonable clarity, is scarcer than a comparable diamond, and the record prices per carat reflect that. Ruby sits at the high end of the ladder in Which Gemstones Are Actually Rare?, and it earns the position.
The scarcity is specifically about size and clarity together. Chromium-rich corundum grows strained and included, so small rubies of good color are attainable while large clean ones are extraordinarily difficult to find. That is the real reason ruby prices climb so steeply with carat weight, more steeply than almost any other gem. As always, we make no claims about future value, on ruby or on anything else. These are pieces to wear and keep.
How ruby wears
Ruby measures 9 on the Mohs scale, tied with sapphire and second only to diamond, with no cleavage plane to split along. As a material it is superb for daily wear, and a ruby ring can be worn for decades without dulling.
The caveat is specific to the individual stone rather than the species. Because ruby is so commonly included and fractured, a heavily included stone has internal weaknesses that a flawless one does not, and a glass-filled stone is fragile in ways the mineral itself never is. A clean, heated ruby is one of the toughest gems you can own. Browse Ruby Rings for the pieces built around a center stone, or the full Ruby Jewelry collection for everything we currently have.
Caring for ruby
Warm water, mild soap, and a soft brush is always safe. Untreated and heat-treated rubies tolerate ultrasonic cleaning well, but a glass-filled or dyed stone absolutely does not, and neither does a heavily fractured one. If you are not certain which you own, check the appraisal, and default to warm soapy water.
Keep acids away from any ruby, including lemon juice and household descalers, and tell your jeweler what the stone is before any repair involving heat. Ruby is hard enough to scratch nearly everything else in your box, so store it separately.
How we document every ruby piece
Every piece arrives with a gemological appraisal that identifies the stone, records carat weight and natural origin, and states any treatment plainly, filling included. It is a grading and identification document, which is why it carries no dollar figure. That is deliberate. With a stone that has a synthetic twin, two historical impostors, and a widespread filling treatment, having the identification in writing is the whole point.
Styling ruby
Yellow gold is ruby's traditional partner and still its most flattering, because warm metal amplifies the red rather than competing with it. White gold and sterling do the opposite, cooling the setting so the red reads sharper and more modern. Rose gold sits somewhere in between and suits lighter, pinker stones.
Ruby pairs beautifully with white diamonds, which is why the combination has been a standard for centuries: colorless brilliance next to saturated red makes both look better. Because fine ruby climbs steeply in price with size, this is a stone where a smaller, better center is usually the wiser buy than a larger, duller one, the opposite of the advice we gave for tanzanite and amethyst.
Ruby is the July birthstone and the traditional gift for a fifteenth and fortieth anniversary. For a broader tour of the color families we carry, start with A Guide to Colored Gemstones, and our sapphire guide covers ruby's twin in every other color.
Buying a one-of-a-kind ruby piece
Every piece in our ruby collection exists once. When one sells it is gone, so the piece you are weighing is the piece, not a sample that can be reordered. Orders ship free and fully insured and arrive in about 5 to 7 days, and you have a 7-day window to inspect the piece in person once it lands. We walk through the whole process, including the honest part about who pays return shipping, in Buying One-of-a-Kind Jewelry Online.
Frequently asked questions
What is the difference between a ruby and a sapphire?
Only color. Both are the mineral corundum. Red corundum is called ruby, and corundum of every other color is called sapphire. Chromium is what makes ruby red.
What does pigeon's blood mean?
It describes the most prized ruby color: a vivid, pure red with a slight blue rather than orange undertone. Some gem laboratories now issue it as a formal color grade, but used casually by a seller it is a description rather than a certification.
What is a glass-filled or composite ruby?
Heavily fractured low-grade corundum whose cracks have been filled with lead glass to make it look transparent. It is far less durable than a normal ruby, can be damaged by household acids, ultrasonic cleaners, and a jeweler's torch, and must always be disclosed. Any filling on a piece we sell is stated on its appraisal.
Are rubies heat treated?
Most are. Heating improves color and clarity, the change is permanent and stable, and the stone remains natural and earth-mined. Untreated rubies with fine color are uncommon and priced accordingly.
Is ruby hard enough for everyday wear?
Yes. At 9 on the Mohs scale with no cleavage plane, ruby is second only to diamond in hardness. The exception is a heavily fractured or glass-filled stone, which needs gentler handling.
Start with the collection
When you are ready, Ruby Jewelry holds every ruby piece we currently have. Every one is natural, documented, and the only one of itself.
