Big loose lab rubies on Amazon
Big loose lab rubies are one of the best buys on Amazon: a lab-grown ruby is the same mineral as mined ruby (red ), sold as lab-created ruby, and a stone of 5, 10 or even 30 carats costs about what a meal out does. Look for listings that say "lab created", "synthetic" or "created" ruby, or "red corundum", and pick the size in millimetres: a 10 mm round is roughly 4 to 5 carats. Skip any cheap listing that calls a large ruby "natural", "unheated" or "certified".
How we pick: We list a stone only when its own listing calls it synthetic, created or lab-grown ruby or red corundum and gives the size in millimetres. Every option had an Amazon price and was in stock when we checked on 17 October 2026. Grades and certificates on a listing are the seller’s claims.
Amazon prices as of . Prices and availability are accurate as of that date and time and are subject to change; the price shown on Amazon at the time of purchase applies.
Big oval, 14x10 to 30x20 mm
Best for: The showpiece for a gem tray
Ovals show the most face for their weight and the colour is richest through the long axis. The biggest faceted lab rubies we found are ovals.
Look for
- Labelled synthetic, created or lab ruby, or red corundum
- Size given in millimetres
- Even red colour through the stone
Gryrigns lab ruby, oval, 20 x 15 mm, 20.5 ctabout $30on Amazon → 
Gryrigns lab ruby, oval, 30 x 20 mm, 48.3 ctabout $55on Amazon → Big round, 10 to 18 mm
Best for: Maximum sparkle
The brilliant cut returns the most light, so a big round is the most dazzling way to show a lab ruby.
Look for
- Round brilliant cut
- A 10 mm round is about 4 to 5 carats, 14 mm about 12
Gryrigns lab ruby, round, 18 mm, 22.5 ctabout $30on Amazon → 
uGems created ruby, round, 14 mmabout $35on Amazon → 
Tianzuan lab ruby, round, 14 mmabout $30on Amazon → Emerald cut, 10x8 to 20x15 mm
Best for: Colour over sparkle
Lab ruby is clean enough for a step cut, which shows the depth of the red rather than flashes of light.
Look for
- Step cut with cut corners
- Clean stone: step cuts show
Gryrigns lab ruby, emerald cut, 20 x 15 mm, 29.8 ctabout $35on Amazon → 
Instagem lab ruby, emerald cut, 12 x 10 mm, about 7.5 to 9 ctCut from Swiss synthetic rough, per the listingabout $45on Amazon → Pear, 10x8 to 18x13 mm
Best for: A stone to have set as a pendant
The pendant shape: any jeweller can set a big pear as a necklace.
Look for
- Symmetrical shoulders
- Point not chipped
CHINALUSTER lab ruby, pear, 13 x 9 mm, 5 ctabout $25on Amazon → 
Tianzuan lab ruby, pear, 16 x 12 mmabout $30on Amazon → Listings worth a look
Chosen for clear labelling of the stone and metal, read off each listing on the day shown. Details and prices change; the listing is the final word.
Gryrigns oval synthetic ruby, 10x8 to 30x20 mm
about $20
The listing says
- Synthetic ruby (red corundum), oval
- Machine cut, sizes 10x8 mm up to 30x20 mm
The biggest sizes we found for a faceted lab ruby: a 30x20 mm oval is a true showpiece for a tray.
See this listing on AmazonGryrigns round synthetic ruby, 10 to 18 mm
about $20
The listing says
- Synthetic ruby (red corundum), round brilliant
- Machine cut, sold by size from 10 to 18 mm
Honestly labelled "synthetic ruby, red corundum". A 10 mm round ruby is roughly 4 to 5 carats; 18 mm is well over 20.
See this listing on AmazonGryrigns emerald-cut synthetic ruby, 10x8 to 20x15 mm
about $30
The listing says
- Synthetic ruby (red corundum), emerald cut
- Sizes 10x8 mm up to 20x15 mm
A step cut shows the stone's colour and clarity rather than sparkle; lab ruby is clean enough to carry it.
See this listing on Amazon
Gryrigns pear synthetic ruby, 10x8 to 18x13 mm
about $15
The listing says
- Synthetic ruby (red corundum), pear shape
- Sizes 10x8 mm up to 18x13 mm
The pendant shape: a big pear is the easiest large ruby to have set as a necklace.
See this listing on AmazonBefore you buy: the listing checklist
- Labelled lab-created, created, synthetic or lab-grown ruby, or red corundum. Those are honest labels.
- Not "natural", "unheated" or "certified" at a lab-ruby price: a large natural ruby costs thousands.
- Size in millimetres; carat weight on budget listings is often an estimate.
- Returns accepted, so you can check the colour in daylight.
Frequently Asked Questions
Is a lab ruby a real ruby?
It is the same mineral as mined ruby (red corundum, coloured by chromium), with the same hardness ( 9), sold as lab-created ruby. In the US the word ruby on a lab stone must be immediately preceded by "laboratory-grown", "laboratory-created", "[manufacturer name]-created" or a phrase of like meaning (16 CFR 23.25), which is why the honest listings say so. Sellers may not call a lab stone real or genuine (16 CFR 23.27).
How many carats is a 10 mm ruby?
Roughly 4 to 5 carats for a round brilliant. Ruby is denser than diamond, so a ruby weighs more than a diamond of the same size. See our ruby size chart.
Do lab rubies glow under UV light?
Many do, strongly: chromium makes ruby fluoresce red under ultraviolet, and flame-fusion lab rubies usually glow brightly. Some mined rubies do too, so a glow proves it is ruby-like, not whether it is lab-grown.
Sources
- US FTC Guides for the Jewelry Industry, 16 CFR 23.25: lab-grown, synthetic and simulated stones
- 16 CFR 23.27: “real”, “genuine” and “natural”
- GIA: ruby care and cleaning (corundum is 9 on the Mohs scale)
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