What is lab-grown white sapphire, and how does it compare with a lab diamond in silver?

ZKZ Editorial TeamMain answer · Product & gemmology desk

They are different materials. A lab-grown diamond is diamond, while lab-grown white sapphire is a colourless corundum, which is softer on the Mohs scale and not sold or described as a diamond. Both are lab-grown, and both should be named as such in a listing.

What we verified

Fact The US National Park Service Mohs hardness scale lists diamond as 10 and corundum as 9, and describes hardness as a mineral's relative resistance to scratching.

Fact GIA says durability has three parts: hardness, toughness and stability, and that hardness means how well a gemstone resists scratches and abrasion.

Fact The FTC Jewelry Guides (16 CFR 23.12) define a diamond as a mineral consisting essentially of pure carbon crystallized in the isometric system, with hardness of 10, and say it is deceptive to use the unqualified word "diamond" for anything that does not meet the definition.

Fact 16 CFR 23.25 says words such as "gem", "gemstone", "birthstone" or the name of a stone, used for a laboratory-grown stone, should be preceded with equal conspicuousness by "laboratory-grown" or a similar term.

How to compare

Our advice Compare appearance in person or in close-up video, and ask for the stone type, size and any report.

Our advice Expect a softer stone to show wear sooner, particularly in a ring worn daily.

It depends Sapphire may suit a pendant or earrings that see less knocks, while a diamond suits a ring worn daily.

Questions to put to a seller

• What exactly is the stone, and is it described as lab-grown?
• What is its size and weight, and is there a report?
• How should I clean it, and is it safe in an ultrasonic cleaner?
• What happens if it chips or scratches?

Our advice Ask for a close-up video of the stone in daylight, since photographs vary in colour and brightness. If a price seems very low for the stone described, find out why before buying.

Uncertain We did not verify the optical properties of white sapphire or the price gap between the two, so we make no claim about sparkle or cost.

Related reading: What colour grade is enough for a lab diamond set in white-plated silver? · Lab Grown Diamond Earrings in Silver: Buying Checklist

Sources

• U.S. National Park Service, Mohs hardness scale
• GIA, Diamond care and cleaning
• 16 CFR 23.12, FTC Jewelry Guides: definition and misuse of the word "diamond"
• 16 CFR 23.25, FTC Jewelry Guides: misuse of "ruby", "sapphire", "emerald", "birthstone", "gem" and similar words

Fact = stated by the cited source. Our advice = editorial recommendation. Uncertain / it depends = limits of what can be said in general.