Field report · 401
Identifying common stone imitations
Glass for opal, dyed quartz for jade, plastic for amber — common imitations and how to spot them.
The vast majority of imitation stones on the market are honestly labeled — "imitation amber" or "simulant jade." Some are not. Knowing the common imitations and basic identification tests prevents disappointing surprises.
Glass imitations
Glass is the most common imitation, especially for transparent colored stones.
- What's imitated: sapphire, ruby, emerald, aquamarine, citrine, amethyst, peridot, tourmaline — anything transparent and colored
- Identification: glass shows different optical properties. Most natural transparent stones are doubly refractive (split light into two rays); glass and cubic stones like spinel are singly refractive. A polariscope reveals this in 10 seconds.
- Inclusions test: natural stones have growth inclusions; glass has gas bubbles (often round, sometimes elongated). Look under 10x loupe.
- Hardness: glass is Mohs 5-6; most gemstones are 7+. A glass imitation can be scratched by quartz; a natural sapphire can't.
- Specific gravity: glass is typically 2.4-2.6; most gems are higher
Plastic imitations
Plastic mimics amber, jet, ivory, coral, turquoise.
- Hot-pin test (carefully!): a hot pin against natural amber will release a pine-resin smell. Plastic releases a melted-plastic smell. (Test in an inconspicuous area; this is destructive at the test point.)
- Specific gravity: amber floats in saltwater; plastic doesn't (usually)
- Static: amber rubbed on cloth attracts paper bits; some plastics don't
- Color uniformity: natural amber has natural variation; molded plastic is often uniformly colored
Stone-stone imitations
Sometimes one stone is used to imitate another more valuable one.
- Green glass / dyed quartz / dyed jadeite imitating natural jadeite — extensive market in fake jade
- Heat-treated synthetic spinel imitating various colored stones
- Hydrothermal-grown emerald at natural-emerald prices
- Synthetic ruby/sapphire (Verneuil, Czochralski, hydrothermal) — undetected without lab equipment in many cases
Reconstituted and pressed stones
"Reconstituted" means powdered natural stone bonded with resin and re-formed.
- Reconstituted malachite — common, low-cost; flat banding without 3D depth
- Reconstituted turquoise — common; uniform color without natural matrix variation
- Pressed amber — sometimes called "ambroid"; small amber pieces fused under heat and pressure
Tests anyone can perform
- Loupe (10x) — $15-30; reveals inclusions and surface features. Most important single tool.
- Refractometer — $50-200; measures refractive index; identifies species. Requires some practice.
- Polariscope — $20-50; distinguishes singly-refractive from doubly-refractive. Quick and conclusive for many ID issues.
- Specific gravity test — $80-200 for a setup; measures density. Definitive for many identifications.
- Chelsea filter — $20-40; reveals chromium presence (separates synthetic from natural emerald, identifies some treated stones)
When in doubt
For a purchase above $500, lab certification is the answer. The cost is small compared to buying a substantially mis-identified stone. For lower-value purchases, focus on buying from reputable sellers — sellers who answer questions, provide documentation, and have something to lose from misrepresentation.