Moissanite vs Diamond — The Real Differences in 2026

Short answer: Moissanite and diamond are two different minerals. Moissanite is silicon carbide (SiC) — hardness 9.25 on the Mohs scale, with double refraction of light. Diamond is pure carbon (C) — hardness 10, with no double refraction. The difference is visible under a 10× loupe in seconds. Moissanite has its legitimate uses; it simply is not a diamond.

What is moissanite

Moissanite is the mineral silicon carbide (SiC). It was discovered in 1893 by the French chemist Henri Moissan while examining a meteorite crater in Arizona. Natural moissanite is extremely rare; almost all moissanite on the market today is laboratory-synthesized.

As a gemstone, moissanite has its legitimate uses:

• High hardness (9.25 on the Mohs scale) — resistant to scratching in daily wear
• High refractive index — very bright sparkle
• Accessible price — roughly a quarter of the price of a lab-grown diamond
• Heat-insensitive under standard conditions

Moissanite is a real stone with its own identity. Karat Bulgaria respects it as a material. The issue in the market is not moissanite itself — it is when moissanite is presented as a diamond.

What is a diamond

A diamond is pure carbon (C), crystallized under high pressure. It is the hardest known natural material — 10 on the Mohs scale. Diamonds are certified by IGI or GIA using the methodology of the 4 Cs — carat, color, clarity, cut.

In 2018 the U.S. FTC removed the word "natural" from the definition of "diamond." Lab-grown and mined diamonds are identical in chemical composition, crystal structure and physical properties. Both are "diamond" — moissanite is not.

Key differences

Property	Diamond	Moissanite
Chemical composition	Carbon (C)	Silicon carbide (SiC)
Mohs hardness	10	9.25
Refractive index	2.42	2.65–2.69
Double refraction	No (isotropic)	Yes (anisotropic)
Dispersion (fire)	0.044	0.104
Certification	IGI / GIA	Typically none
Price per ct at Karat	~€1,074 (lab-grown D/VVS1)	~€245
Market value	High and stable	Low and stagnant

Visual differences — what is visible under a loupe

The most reliable way to distinguish moissanite from diamond is with a 10× gemological loupe. Moissanite is anisotropic — light refracts twice when passing through the crystal. This means that when looking through a facet, internal edges appear "doubled" — almost blurred.

Diamond is isotropic — it refracts light equally in all directions. Internal edges are crystal-clear, with no doubling.

Other visual indicators:

• Fire (dispersion): moissanite splits light into a rainbow of colors more strongly than diamond. At first glance it can look "brighter," but the expert eye recognizes excessive fire as an indicator of moissanite.
• Heat reaction: moissanite conducts heat differently from diamond — electronic gemological testers distinguish the two stones instantly.
• Weight vs size: at the same size, moissanite weighs about 10% less than diamond.

At Karat, our specialists examine every stone with a 10× loupe in the client's presence before finalizing the purchase.

Price and market value

Moissanite is significantly more accessible than diamond. Comparison at Karat (May 2026):

• 1 ct round moissanite: around €245
• 1 ct round lab-grown diamond D/VVS1 with IGI certificate: around €1,074
• 1 ct round mined diamond D/VVS1: around €3,800

The price difference reflects the difference in material — not "cheaper diamond," but a different stone with a different market position.

When moissanite is the appropriate choice

Moissanite has legitimate applications in modern jewelry. It is appropriate when:

• The budget is strictly limited and the buyer knowingly chooses moissanite, not diamond
• The stone is for secondary jewelry (second ear piercings, additional band)
• Wear is daily and intensive and the buyer does not want the risk of losing a more valuable stone
• The stone is for a child or adolescent — where high value is not justified

When diamond is the better choice

For an engagement ring, wedding band or heirloom piece, diamond remains the standard. The reasons:

• Certifiability: IGI and GIA certify diamonds using established methodology. Moissanite typically has no certificate from leading gemological laboratories.
• Long-term value: diamonds retain a larger share of market value over time; moissanite appreciates significantly less in resale.
• Symbolism: diamond is globally recognized as the symbol of engagement and marriage. Moissanite is newer to the market and lacks the same cultural weight.
• Lab-grown diamond as a compromise: the same stone as mined, at roughly one-third the price, with the same IGI certificate — often the better alternative to moissanite for a buyer with a more limited budget.

How to identify the stones yourself

Before buying a stone presented as a diamond, perform these five checks:

1. Require an IGI or GIA certificate. A real diamond — lab-grown or mined — always has a certificate from a recognized laboratory. If the seller has no certificate, the stone is most likely not a diamond.
2. Ask for a 10× loupe. Every serious jeweler has a loupe and will let you examine the stone. Look for "doubled" internal edges — a sign of moissanite.
3. Ask for an electronic tester. Diamond testers distinguish diamond from moissanite in seconds.
4. Check the price against the market. If a "diamond" of 1 ct is offered below €750, it is certainly not a certified diamond.
5. Require a written guarantee. A serious jeweler provides a written declaration of the material and characteristics of the stone.

The Karat approach

At Karat Bulgaria we do not offer moissanite. This is not because it is a "bad" stone — but because our focus is lab-grown and mined diamonds with IGI certificates. When a client asks about moissanite, we explain the differences clearly and direct them to a retailer that offers it openly.

What Karat does not do: we do not present one stone as another. When we show a lab-grown diamond, the client receives an IGI certificate. When we show a mined diamond — the same standard. Transparency is the standard of our boutique.

We receive clients every month who arrive with a ring purchased elsewhere as a "diamond" that turns out to be moissanite. This is not the stone's fault — it is a matter of honesty in the sale. At Karat we would always prefer to lose a sale than to sell something as what it is not.

What to remember

Moissanite and diamond are two different minerals with different chemical compositions, hardness levels and market positions. Moissanite has legitimate applications — but it is not a diamond. For an engagement ring, Karat Bulgaria's recommendation is a lab-grown diamond with an IGI certificate: the same stone as a mined one, at a more accessible price, with full traceability. Always require a certificate from a recognized laboratory.