Lab-grown vs natural: what is actually different
A lab-grown sapphire is corundum, aluminium oxide, exactly what a mined sapphire is; a lab diamond is carbon in the diamond lattice, exactly what a mined diamond is. Hardness, refractive index, the way light moves through it: identical, because it is the same substance. What differs is where the crystal formed, what got trapped inside it while it grew, what it costs, and what someone will pay you for it later. That last one is close to nothing for both, under about a carat.
Same mineral, different birthplace
Mined corundum grew over millions of years in rock; lab corundum grows in days to months in a furnace by one of several methods. Flame fusion (Verneuil, 1902) drips powdered alumina through a flame onto a growing boule; it is the cheapest, and it is what loose lab sapphire and ruby sold for a few dollars a stone on Amazon are. Flux and hydrothermal growth are slower and dearer and produce stones that look more like mined material inside. Lab diamonds grow either by HPHT (high pressure, high temperature, mimicking the mantle) or CVD (a carbon-rich gas depositing onto a seed plate); the lab diamond melee we ordered is listed as either.
What you can see, and what you cannot
You cannot see the difference by eye. Mined stones usually carry inclusions, colour zoning and silk; lab stones are usually cleaner and more evenly coloured, which is why a dead-even, glass-clear blue in a cheap "sapphire" is itself a hint that it grew in a furnace. Flame-fusion corundum can show curved striae under 10x magnification, the one tell a loupe can find; mined corundum grows in straight angular zones. Lab diamonds are separated from mined ones only by laboratory instruments that read fluorescence patterns and trace nitrogen; a thermal diamond tester says "diamond" for both, and says "diamond" for moissanite too unless it is the electrical kind.
Price and resale
Lab corundum costs a few dollars a carat in flame-fusion grades; mined sapphire of good colour costs hundreds to thousands. Lab diamond has fallen to a small fraction of mined diamond and keeps falling as production scales. The honest consequence: buy lab stones to wear and to set, not as a store of value. Mined stones under a carat are not much of a store of value either, whatever the counter says.
What to buy for what
- A stone to set yourself: lab corundum, oval or cushion, calibrated to a standard mounting size. Cheap enough to ruin one learning.
- Pave or accent stones: lab diamond melee, sold by millimetre size; run a tester on arrival.
- A big white stone on a budget: moissanite, which is not a diamond and has more fire than one; see moissanite vs lab diamond.
- Something to hold value: none of the above. A graded mined stone of good colour over a carat, from a dealer, with a report.
Frequently Asked Questions
Can a jeweller tell lab-grown from natural?
Not by eye, and usually not with a loupe. Lab diamonds are separated from mined ones with laboratory instruments that read growth patterns and trace elements; lab corundum from the cheapest growth method (flame fusion) can show curved growth lines under magnification that mined stones never have, which is the one tell a good loupe user can find.
Do lab-grown stones lose value?
They have little resale value to begin with, and lab diamond prices have fallen steeply as production scaled. Buy lab stones to wear, not to hold; that is also true of most mined stones under a carat.
Is "lab-created" the same as "simulated"?
No. Lab-created means the same mineral, grown rather than mined: lab sapphire is corundum, lab diamond is carbon. Simulated means a different material that looks similar: cubic zirconia and moissanite simulate diamond, glass simulates everything. A listing that says "created" without "lab" is worth a second read.