The Fakes: Diamond Simulants — and Why “Real vs. Fake” Is the Wrong Frame

Change log: Wave 4 first pass. A18 is the most “practical” of GIA’s assignment lists; every entry is an identification-method paper, so the module is organized as a property-ladder rather than an article-by-article recap.

Sixty years of look-alikes, in five sentences

The A18 timeline, read as a story of escalation: 1957 — Benson catalogs “diamond substitutes” (glass, strontium titanate, YAG-era materials: the soft-optics zoo the pre-CZ market traded); 1978 — Liddicoat & Koivula describe cubic zirconia arriving as a production material (“synthetic cubic stabilized zirconia”), not a lab curiosity; 1981 — Nassau updates CZ and Hobbs offers “a simple approach” to separation, the trade’s first mass-detection doctrine; 1990s — Kammerling 1991 examines non-transparent “CZ” from Russia (i.e., fakes outside the normal spec), and 1997 — Nassau et al. publish synthetic moissanite as a new diamond substitute: the first simulant to beat the thermal tester; 2000s–2010s — the arms race turns combinatorial: Shigley et al. 2012 characterize coated CZ (“Diamantine”) — a soft material wearing a thin diamond-like film — while Choudhary 2013 flags boron carbide imitating black diamond; Zhou 2015 and Song et al. 2016 document synthetic moissanite in melee — including moissanite made to imitate lab-grown colored diamonds, the substitution hiding inside a substitution. The pattern every one of these papers encodes: every detector is a property test, and every new material picks off the detectors one by one.

The property ladder (what a professional actually uses)

Simulant separation is not tricks; it’s a decision tree over physical properties (textbook values; ranges are standard-reference level — any number you print on a card):

The screening narrative you can trust in a store (from GIA’s own verified video narration, GIA-03): “before even stepping into the four Cs, the diamond is tested to determine whether it is natural or lab-grown” — and every report system sits behind that gate. For simulant control the same logic applies one level down: thermal/electrical probes at intake, loupe double-check on anything the probe calls “pass,” and the polariscope/doubling rule as the tie-breaker when moissanite is in play.

The disclosure conversation: retire “fake,” install “different material”

The vocabulary problem is a liability problem. “Fake” accuses; it also teaches the customer that the category CZ exists to deceive — which your own jewelry case disproves (most CZ sold is disclosed fashion jewelry). The honest, sales-safe frame:

• Simulant = a material that simulates diamond appearance (CZ, moissanite, glass, coated goods). It is a product, not a crime.
• Synthetic (lab-grown) = a real diamond, made by another process (M11). Never call it “fake”; that’s legally imprecise and commercially wrong.
• Natural diamond = the M02/M03 story; its trade advantage is provenance and resale norms, not “realness.”

So: the buyer of a CZ ring is buying look; the buyer of a lab-grown is buying material (identical physics, different market); the buyer of a natural is buying material + history. Every complaint the A18 papers exist to answer — undisclosed moissanite melee in a bracelet (Zhou 2015), a coated stone wearing two identities (Shigley 2012) — is a disclosure failure, not a material failure. That’s also the FTC-frame (Overton 2004, A19 list — M12). Your job on the floor is to make the three sentences above automatic.

The melee problem (what the 2013–2016 papers are really about)

Single-stone detection is solved; parcel and repair detection is the open wound the later A18 entries document: loose melee runs through the market untested; a repair or re-polish can swap one stone into a tray of twenty; the “Diamantine” and “synthetic moissanite” waves specifically target the colored melee niche where certificates never existed. Practice consequences:

1. Intake screening on parcels (Dieck et al. 2016, “Analysis of Yellow Diamond Melee for Color Treatment and Synthetics,” G&G 52:1 — title-level here): if your shop repairs and a tray looks too clean/too sparkly for its era, screen it.
2. The loupe at 10× finds the two big tells: facet-junction doubling (moissanite), and lead-light orange-flash in fracture/rim (filled or coated). Both are A18/A19 paper abstracts’ exact themes.
3. Tell the repair story: customers should hear “we screen every stone we touch,” which is precisely the promise the GIA video’s gate makes at lab scale.

Self-check

1. Order the five properties that separate CZ from diamond by the loupe route (no electronics).
2. Why did moissanite “break” the industry default tool, and what replaced it? (thermal → conductivity; multi-testers)
3. Name the two A18-era combination frauds and their telltales. (coated CZ — flash/abrasion, interferometry at lab; moissanite-as-synthetic-colony — polarization/doubling + tester cross-check)
4. Give the three-sentence disclosure frame in your own words (simulant/synthetic/natural).
5. Which is riskier for a repair shop: a loose 2 ct round or a sealed bracelet of melee — and why? (the melee: no cert, untested intake, swap opportunity)

Further reading (A18)

Full annotations in `references/annotated-bibliography.md`. Priority reads: Nassau 1997 (30 minutes that explain the whole detector-arms-race logic); Shigley 2012 Diamantine (coated-goods methodology); Song 2016 (modern layered fakery). Pair with M12 (fillings/coatings overlap) and M11 (lab-grown vs. simulant language discipline).