Lab rough
Buy lab gem rough
Every cut lab gem starts as a crystal straight out of a furnace or a press. These are the real ones you can buy on Amazon: whole ruby and sapphire up to 600 carats for under $100, small HPHT diamond crystals, and colour-change rough. Cutters facet them; collectors keep them as they are. Photos are the sellers' own, checked in stock in October 2026.
Want them cut instead? See the lab gem catalog and the biggest lab gems. Curious how each one is grown? How lab gems are grown.
Flame fusion (Verneuil)
A whole flame-fusion ruby boule
This is what a lab ruby looks like the moment it comes off the furnace: one single crystal shaped like a fat crayon, called a boule. Powdered alumina with a pinch of chromium falls through a hydrogen and oxygen flame hotter than 2,000 C, melts, and lands drop by drop on a slowly sinking ceramic rod. The crystal grows upward in a matter of hours, and the flame leaves the outside slightly rippled and dull. It is dark because you are looking through a thick block; cutting thin faceted stones from it lets the light back out as red.
Gryrigns lab ruby rough, 600 ct, about $85
Flame fusion (Verneuil)
A boule split in half
A boule cools fast and is full of internal strain, so it is usually split lengthwise, often with nothing more than a tap. One side is the rounded outer skin from the furnace; the other is the bright, glassy break face. Cutters orient their stones from that flat face. Inside, the crystal has like the layers of an onion, which is how a gemologist later knows a cut stone grew in a flame.
Gryrigns lab ruby rough, 250 ct, about $40
Flame fusion (Verneuil)
Another split boule, bigger
The same story at a larger size: a half boule with a long, clean split face. A cutter keeps only part of the weight, because most of a rough piece ends up as dust on the lap, so a 350 carat boule becomes a handful of finished stones.
Gryrigns lab ruby rough, 350 ct, about $55
Flame fusion (Verneuil)
A blue sapphire boule with its domed top
Sapphire is grown the same way, with iron and titanium in the powder instead of chromium. Look at the rounded end: that dome is the growing surface, where the molten drops landed last. It looks almost black because blue sapphire absorbs so strongly through a thick piece; thin cut stones show the royal blue.
Gryrigns lab sapphire rough, 150 ct, about $65
HPHT (high pressure, high temperature)
Lab diamond crystals straight out of the press
Lab diamond does not come from a flame. Carbon dissolved in molten metal is squeezed in a press at around 5 to 6 gigapascals, the pressure 150 kilometres down, at 1,300 to 1,600 C, and diamond crystallises out over hours to days. It grows cube and octahedron faces at the same time, which gives these blocky, many-sided crystals. The yellow is nitrogen, from the air and the raw materials, trapped in the lattice; crystals like these are made by the tonne for cutting tools and abrasives. Colourless gem diamonds need the nitrogen kept out.
Lab-grown yellow diamond rough, single crystal, about 0.26 ct, about $35
Kyropoulos and other industrial methods
Lab sapphire with no colour at all
Most lab sapphire on earth is never a gem. It is grown colourless, in crystals weighing tens of kilograms, then sawn into windows, phone camera covers, watch crystals and LED substrates. This little disc is the same aluminium oxide as a royal blue sapphire, minus the iron and titanium. Scratch it with steel and nothing happens: only diamond and moissanite are harder.
Optical sapphire window, 10 mm, 1 mm thick, about $30
Czochralski pulling
Pieces of a pulled crystal: silicon
The Czochralski method dips a seed into a molten bath and pulls a crystal up out of it, rotating slowly. Some lab ruby, sapphire and alexandrite are grown this way, but its real job is silicon: almost every computer chip starts as a pulled silicon crystal the size of a person. These glassy grey shards are broken offcuts of that kind of crystal, sold as monocrystalline. They show the shell-like fracture of a single crystal, with no grain boundaries.
Monocrystalline silicon chunks, 100 g, about $15
Acheson furnace (sold as natural, but it is not)
Furnace silicon carbide: the rock moissanite comes from
These spiky rainbow clusters are often listed as natural carborundum. They are not: natural (moissanite) exists only as microscopic grains, first found in a meteorite crater in Arizona. These grow in an industrial furnace, invented by Edward Acheson in 1891, where sand and carbon are baked at about 2,500 C to make abrasive grit. It is the same compound as moissanite, the gem, which is grown far more slowly and cleanly. The rainbow is a thin surface layer, like the colours on bismuth. A lab crystal people buy as a natural mineral, and a lesson in reading listings.
Justinstones rainbow carborundum with stand, about $13
What it costs to cut lab rough, and is it cheaper than buying the stone cut?
Short answer: no. Lab ruby rough costs about 15 cents a carat from sellers with reviews (a 600 carat boule is about $85; about 44 cents for blue sapphire), so the stone itself is almost free. What costs money is the cutting. A cutter keeps only about 20 to 35 percent of the rough weight; the rest is ground to dust. So a 5 carat finished ruby needs 15 to 20 carats of rough, about $3 worth, and a 30 carat stone needs about 100 carats, about $15 worth.
| Route | 5 ct stone | 30 ct stone | How the price works |
|---|---|---|---|
| Buy it already cut | about $25 | about $35 | A CHINALUSTER 5 ct pear, or the Gryrigns 29.83 ct emerald cut. Machine-cut, ready to set. |
| Raw rough + a commercial cutting house | about $35 to $65 | about $200 to $250 | About $6 per finished carat, or a per-stone fee; often overseas. |
| Raw rough + a US custom cutter | about $325 | about $1,400 | $85 a stone plus $35 a carat, plus 25 percent because is hard. |
| Raw rough + a precision cutter | about $500 to $650 | $3,000 or more | $99 to $129 per finished carat, or $299 an hour. |
| Raw rough + cut it yourself | about $3 of rough | about $15 of rough | Plus a starter machine, about $260 to $500 once, and your time. |
Buying a lab stone already cut wins by a wide margin, because the factories that grow corundum also cut it by machine in huge batches, for very little per stone. Paying a person to cut one stone by hand costs 10 to 100 times what the stone is worth. Raw lab rough makes sense for three things:
- Learning to facet. A mistake costs cents, which is why hobby cutters practise on lab corundum before touching anything mined. A starter machine pays for itself against a custom cutter after one or two stones, though never against buying cut.
- A one-off design you cannot buy ready-made: an unusual shape, a precision cut with more facets and better light return than a machine cut, or a stone sized to an heirloom setting.
- Keeping it raw. A boule is a beautiful specimen as it is, and the cheapest way to own a large single crystal.
If you want to cut it yourself: the starter kit
VEVOR gem faceting machine with angle manipulatorThe entry-level faceting machine: a variable-speed lap plus an arm that holds the stone at an exact angle.about $265 on Amazon → 
Mxmoonant gem faceting machine, 96 index wheelA step up, with a 96-tooth index wheel for more facet positions.about $400 on Amazon → 
HARFINGTON diamond lap set, 120 to 3000 grit, 6 inchNine laps from coarse cutting to fine pre-polish. Corundum is hard, so diamond laps do the work.about $40 on Amazon → 
JuxLux lapidary dop wax, 140 gHolds the stone on the dop stick while you cut.about $10 on Amazon → 
GemOro 10x triplet loupeCheck every facet meeting point as you go.about $17 on Amazon → The two lab ruby rough listings that look cheapest per carat are copies of the Gryrigns titles from new sellers with no reviews (about 10 cents a carat), and the huge 450 to 2,250 carat "lab created" lots come from a seller that also sells 2,000 carat "lab emerald" for under 2 cents a carat, which cannot be real . We stick to sellers with a record. Cutting prices come from published price lists, some a few years old, so ask any cutter for a written quote first: Lambert, Gem Mountain, The Gemstone Artist, International Gem Society on yield.
Lab rough to avoid
- Cheap "lab emerald rough", hundreds of carats for about $20: glass. Real lab emerald costs dollars per carat.
- "CERTIFIED lab-created" rough at absurd weights for the price, such as 2,000 carats of "ruby" for $30, from sellers with no reviews.
- "Natural, untreated" rubies and sapphires of 40 carats or more for $20: no mined stone that size costs that. The site never links sellers who list like this.
- Diamond "rough" with a cut and polish grade: rough has neither, so the listing was copied from a cut stone.
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