How to identify real Moissanites vs lab-grown ones: Expert identification guide

Most moissanite you see in jewelry is lab-grown. Natural moissanite is a geological rarity and almost never appears as a colorless faceted gem. That’s why confusion is common: people ask if a stone is “real” (genuine silicon carbide) or “lab-grown” (how almost all genuine moissanite is made), and some worry it might actually be diamond, cubic zirconia, or glass. This guide explains how to identify genuine moissanite, how professionals confirm it, and what it would take to tell a natural crystal from a lab-grown one.

What “real” means in moissanite

“Real” should mean the chemistry and crystal structure are correct: silicon carbide (SiC), not glass or another simulant. By that definition, lab-grown moissanite is real moissanite. Natural moissanite does exist, but it is extremely rare, usually small, and often greenish. Colorless, jewelry-grade natural moissanite is almost unheard of. If someone offers a large “natural” colorless moissanite, treat the claim with skepticism and ask for a lab report.

At-home checks (non-destructive, fast)

These won’t replace a lab test, but they can help you avoid obvious mistakes and guide your next step.

• Look for facet doubling with a 10× loupe. Moissanite is birefringent. When you view pavilion facets through the crown at a slight angle, facet edges appear doubled or “fuzzy.” Diamonds are singly refractive, so their facet edges stay crisp. Why it works: moissanite splits light into two rays; diamonds do not. Tip: doubling can be hidden if the stone is cut along its optic axis. Rotate the stone and look through several facets, not just the table.
• Rainbow “fire” that looks a bit too strong. Moissanite’s dispersion (~0.104) is more than twice diamond’s (~0.044). You’ll often see bold rainbow flashes, especially under spot lighting. Why it helps: stronger dispersion is a hallmark of moissanite, though high-cut diamonds can still be fiery, so this is suggestive, not conclusive.
• Check for a laser inscription on the girdle. Many lab-grown moissanites are branded and laser-inscribed. Use a loupe and good side lighting. Why it helps: inscriptions can confirm a genuine moissanite brand or model. Absence of an inscription proves nothing.
• Heft test (very rough triage). In the hand, cubic zirconia feels “heavy” for its size (SG ~5.6–6.0). Moissanite is lighter (SG ~3.21), similar to diamond (3.52). Why it helps: it can rule out CZ, but won’t separate moissanite from diamond.
• UV flashlight check. Many moissanites fluoresce greenish to yellow; many diamonds fluoresce blue. Why it helps: the color can hint at moissanite, but both species show variable fluorescence. Treat this as a clue only.
• Avoid scratch tests. Moissanite (hardness ~9.25) can scratch sapphire and glass, but you risk damage and still won’t separate it cleanly from diamond.

Bench tests a jeweler will use

A good jeweler or gemologist can confirm moissanite quickly using simple instruments and magnification.

• Diamond/moissanite multi-tester. Diamond testers measure heat flow; moissanite “passes” as diamond on heat alone because both conduct heat well. A proper multi-tester also measures electrical conductivity. Most moissanites are slightly electrically conductive; diamonds are not. Why it works: it exploits a property moissanite has and diamond lacks. Note: mounted stones and dirty surfaces can cause false readings; pros re-test and clean.
• 10× to 30× microscopy. They look for:
  • Doubling of facet junctions (from birefringence).
  • Characteristic growth features like subtle strain patterns or curved growth lines in some lab stones.
  • Inclusions that fit moissanite (tiny reflective crystals, wisps) instead of diamond’s typical crystals/needles.

  Why it works: optical behavior and inclusion style are diagnostic when seen from the right angles.

• Polariscope/adaptor test. Moissanite shows strong double refraction, blinking light/dark as the stone is rotated between crossed polars. Diamond stays dark (except minor anomalous effects). Why it works: it directly reveals anisotropy.
• Refractometer (spot reading) and reflectivity. Moissanite’s refractive index is high (~2.65–2.69) and shows birefringence (~0.043). Direct contact readings are tricky because RI exceeds typical refractometer limits, but experienced users can get indicative results. Why it helps: diamond is 2.42 and singly refractive.
• Hydrostatic specific gravity. Moissanite ~3.21 vs diamond ~3.52 vs CZ ~5.6–6.0. Why it works: density separates CZ decisively and can support an ID with other tests.
• Raman spectroscopy (definitive). Moissanite (SiC) shows strong peaks around ~796 and ~972 cm⁻¹; diamond shows a sharp line at 1332 cm⁻¹. Why it’s gold standard: it reads the lattice itself. Many labs and some jewelers have handheld Raman units.

Telling natural moissanite from lab-grown moissanite

This is advanced, and in the jewelry trade the answer is almost always “lab-grown.” Still, here is what experts rely on when origin matters.

• Context and plausibility. Natural moissanite crystals are usually tiny, green to black, and found in unusual geological settings (e.g., meteorites, mantle xenoliths). Large, colorless, precision-cut stones offered as “natural” are almost certainly lab-grown. Why it matters: extraordinary claims need extraordinary evidence.
• Polytype identification (Raman/CL). Moissanite comes in different stacking sequences (e.g., 6H, 4H, 15R). Commercial gems are commonly 4H/6H. Natural crystals can show different polytype mixes. Raman spectroscopy, cathodoluminescence, or X-ray diffraction can distinguish polytypes. Why it helps: certain polytype patterns are more consistent with natural or synthetic growth.
• Trace elements and inclusions. Natural stones can contain mineral inclusions, graphite, or features consistent with geological formation. Lab-grown stones may show curved growth, seed-related features, or tiny metallic particles from growth equipment. Why it works: growth environment leaves fingerprints.
• Stable isotope analysis (C, Si). Natural moissanite can show unusual isotopic signatures different from synthetic feedstock. Why it’s decisive: isotopes record origin, but this test is specialized and expensive.
• Professional lab report. A major gemological lab can identify moissanite and may comment on natural vs synthetic indicators. For small, inexpensive stones, the cost may exceed the stone’s value; for important pieces, it’s worthwhile. Why it matters: only a lab can provide defensible documentation.

Common mix-ups: moissanite vs diamond, CZ, and sapphire

• Moissanite vs diamond.
  • Moissanite: birefringent (facet doubling), stronger rainbow fire, slight electrical conductivity, SG ~3.21, RI ~2.65–2.69.
  • Diamond: singly refractive (no doubling), subtler dispersion, electrically insulating, SG ~3.52, RI 2.42.
  • Why people get fooled: heat-based diamond testers misread moissanite as diamond; both are very brilliant.
• Moissanite vs cubic zirconia (CZ).
  • CZ: much heavier for size (SG ~5.6–6.0), softer (~8–8.5), lower brilliance, often shows wear on facet edges.
  • Moissanite: lighter, crisper edges, higher brilliance and dispersion, facet doubling.
  • Quick tells: heft, wear patterns, and magnified doubling separate them.
• Moissanite vs white sapphire.
  • White sapphire: singly refractive, dispersion is low (little rainbow fire), often shows wispy “silk” inclusions.
  • Moissanite: double refraction and strong rainbow fire.
  • Quick tell: lack of doubling and modest fire suggest sapphire.

How to structure a reliable identification

• Step 1: Loupe and lighting. Clean the stone. Use a 10× loupe. Hunt for facet doubling from different angles and any laser inscription.
• Step 2: Multi-tester reading. Use a combined heat/electricity tester. If it reads “diamond” on heat but “moissanite” on conductivity, that supports moissanite.
• Step 3: Microscopy and polariscope. Confirm double refraction and look for moissanite-typical features.
• Step 4: Density or Raman (if needed). Hydrostatic SG can rule out CZ. Raman spectroscopy gives a definitive SiC signature.
• Step 5 (only if origin claim is unusual): Send to a gem lab for polytype/isotope/spectroscopic analysis to evaluate natural vs lab-grown claims.

Buying and documentation checklist

• Ask for a written identification. The invoice should state “moissanite” clearly, with size and cut. If “natural” is claimed, require a lab report.
• Look for brand or model inscriptions. Many makers laser-inscribe the girdle. Photograph the inscription for your records.
• Verify with a jeweler before setting. Identification is easiest loose. Once mounted, metal prongs can complicate testing.
• Know what labs will and won’t do. Major labs can identify moissanite. Grading (like diamond color/clarity scales) is not standardized for moissanite, so expect identification rather than traditional diamond-style grading.
• Return policy matters. If independent testing disagrees with the seller’s claim, you need an exit.

Key specifications (for quick reference)

• Chemistry: Silicon carbide (SiC)
• Hardness: ~9.25 (Mohs)
• Refractive index: ~2.65–2.69; birefringence ~0.043
• Dispersion (fire): ~0.104
• Specific gravity: ~3.21
• Electrical conductivity: Often slightly conductive (varies by stone)
• Raman peaks: ~796 and ~972 cm⁻¹ (vs diamond at 1332 cm⁻¹)

Bottom line

If your goal is to separate moissanite from diamond or CZ, a multi-tester plus a 10× loupe and a trained eye are enough. Look for facet doubling, strong fire, and a conductivity reading. If your goal is to prove a stone is “natural moissanite,” expect to involve a major lab and advanced methods. In the real-world jewelry market, colorless moissanite that is genuine SiC is almost always lab-grown—and that is exactly what most buyers want.