The Tektite Dilemma

Moldavite is a forest-green silica-based tektite formed roughly 15 million years ago by a massive meteorite impact in the Ries Crater in southern Germany. The melted splattered rock landed in the Bohemian region of the Czech Republic, creating the only moldavite field on Earth.

Because of its limited supply and exploding popularity, the mineral market is flooded with cheap, green bottle-glass imitations, mostly produced in factories in China and Southeast Asia.

To ensure you are buying the real thing, you must know how to identify real moldavite using scientific mineralogical tests.

1. The Surface Texture and Luster

Commercial green glass fakes are created by pouring molten glass into molds. This process leaves distinct signatures:

  • Real Moldavite: Possesses a highly complex, rugged, and pitted surface resembling wrinkled tree bark, cratered skin, or flowing water. The finish is satiny or matte, never glassy.
  • Fake Moldavite: Often has a wet, shiny, glossy luster. If it has texture, it is usually regular or repetitive because it was cast in a mold. Look closely for mold seams along the edges of the stone, which never occur in natural tektites.

2. Microscopic Analysis: Lechatelierite and Bubbles

The absolute best way to identify real moldavite is under 10x magnification or a gemological microscope. Look for the following two internal features:

Lechatelierite Inclusions

Lechatelierite is pure fused silica (SiO2). Because moldavite was formed under extreme temperature and pressure, quartz grains in the target rock melted instantly into silica glass threads. Under magnification, lechatelierite appears as:

  1. Wavy, wire-like threads twisting through the green matrix.
  2. They have a different refractive index than the surrounding glass, making them look like clear, fluid veins.
  3. Note: Commercial glass manufacturers cannot replicate lechatelierite threads because their melting temperatures are not high enough.

Gas Bubbles

All tektites contain gas bubbles trapped during rapid cooling.

  • Real Moldavite: The bubbles are elongated, torpedo-shaped, or oval, matching the aerodynamic flow of the flying molten rock.
  • Fake Moldavite: The bubbles are almost always perfectly spherical because commercial glass is melted in stable, atmospheric conditions.

3. Physical Properties Comparison

| Physical Property | Genuine Moldavite | Fake Green Glass | | :--- | :--- | :--- | | Mohs Hardness | 5.5 to 6.5 | 5.0 to 5.5 (varies) | | Chemical Formula | SiO2 + Al2O3 | Variable Soda-lime glass | | Refractive Index | 1.48 to 1.54 | 1.50 to 1.60 | | Specific Gravity | 2.27 to 2.40 | 2.40 to 2.52 |

If you have access to a gemological refractometer or specific gravity testing kit, you can easily distinguish moldavite from heavy leaded glasses.

Conclusion

When shopping for moldavite, avoid deals that seem too good to be true. Look for natural inclusions like lechatelierite under a loupe and check the surface texture carefully.

For more scientific details and research on this topic, you can check out the Mindat.org geological database.