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Moissanite

Last updated: April 2026

All gem-quality moissanite in trade is synthetic silicon carbide (SiC), grown by CVD. Natural moissanite occurs only as microscopic crystals in meteorites and rare terrestrial deposits and is not used as a gemstone. The relevant identification question is moissanite vs. diamond, not natural vs. synthetic moissanite.

Moissanite has a specific gravity of 3.22 and a refractive index of 2.648–2.691, with a Mohs hardness of 9.25. It is uniaxial +.

Physical & Optical Properties

RI Range2.648–2.691
SG Range3.20–3.22
SG Typical3.22
Hardness (Mohs)9.25
Crystal SystemHexagonal
Optic CharacterDR Uniaxial (+)
Birefringence0.043
Dispersion0.104
Fluorescence LWVariable
Fluorescence SWInert
Chelsea FilterInert
PleochroismWeak
ColorsColorless, Green, Yellow Orange, Blue Violet
SpeciesSilicon Carbide
ColorlessGreenYellow OrangeBlue Violet

Measured with a polariscope, a refractometer, a hydrostatic balance, a Chelsea filter, a UV torch, a loupe, a darkfield loupe and a spectroscope — step-by-step for each.

Through the refractometer

Moissanite no reading — over the limit 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 REFRACTIVE INDEX DORead the scale from bottom to top, then look for theliquid’s own faint line near the top. SEEThe field stays dark, with one faint line near 1.81 thatdoes not move when you change stones. MEANSOver the limit — this stone’s index is above the contactliquid’s own, so the liquid is the last thing the instrumentcan still see. That faint line is your proof the instrumentis working rather than dead. It is a RESULT: it eliminatesevery species below 1.81 in one observation. A field darkwith NO line means something else has gone wrong. Computed from gems.json — edge positions are arithmetic, not drawn. RI increases upward; the field above the boundary is the dark one.

Drawn from the refractive index above, on a 1.40–1.81 scale. How to take this reading.

Through the polariscope

Moissanite Blinks 4× per turn (DR) 0° 45° 90° 135° ROTATION BETWEEN CROSSED POLARS Moissanite blinks light-dark four times in a full turn. That is doubly refractive. It does NOT tell you uniaxial from biaxial — that is the optic figure, which needs a conoscope. Computed from optic character and transparency in gems.json. A polariscope separates singly refractive, doubly refractive and aggregate — it does not show the optic sign.

Drawn from the optic character and transparency above. A polariscope separates singly refractive, doubly refractive and aggregate; the optic sign needs a conoscope. How to take this reading.

Specific gravity, and what it rules out

Moissanite SG 3.20–3.22 WHERE IT SITS, AND WHAT ELSE IS THERE 1.0 2.0 3.0 4.0 5.0 SPECIFIC GRAVITY 10 other species in the table overlap this range, so a reading here narrows the field to 11 rather than naming the stone. Combine it with a refractive index to separate what is left. Computed from the specific-gravity range in gems.json. Hydrostatic weighing — the bench method this site recommends; heavy liquids are toxic and regulated. Faint ticks are the other species in the table.

Drawn from the specific-gravity range above, against every other species in the table. How to take this reading.

Through the dichroscope

Moissanite Two colours (dichroic) BEST ORIENTATION ROTATED 45° — THE NULL At its best orientation Moissanite shows colorless in one window and pale bluish-green in the other. Rotate the instrument 45° and the two windows become IDENTICAL — the null. So "both windows the same" means either the stone is singly refractive or you are holding the instrument at the wrong angle, and the only way to tell is to turn it. Computed from pleochroism and pleochroic colours in gems.json. Window tints are derived mechanically from the colour words, not chosen; a neutral pair depicts no colour at all.

Drawn from the pleochroism above. Two windows that match mean either no pleochroism or the wrong angle — turn the instrument to tell. How the dichroscope compares.

Key Differentiators

Natural vs. Synthetic

Synthetic moissanite is commercially available (CVD — Chemical Vapour Deposition (Cree / Charles & Colvard), HTCVD — High-Temperature CVD variants). Distinguishing natural from synthetic typically requires microscopic examination of internal features.

Loupewise Pro includes a two-phase natural vs. synthetic testing protocol for Moissanite.

Common Simulants

Commonly Confused With

Commonly confused with: Diamond.

Treatments

Related Comparisons

Diamond Vs Moissanite

Measurement Guides

How to Identify a GemstoneHow to Measure Specific GravityHow to Use a RefractometerUV Fluorescence Testing

Identifying a moissanite? Loupewise walks through these tests in order — RI, SG, fluorescence, and more.

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Studying for the GIA, FGA, or FEEG practical? Moissanite is one of the 132 species in Loupewise’s drill and exam pool — practice identifying it from its measured properties under timed exam conditions.

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