How to identify Tektite

To correctly identify Tektite (Natural glass (silica-rich)), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Typically black, dark brown, or dark green. Rarely yellowish-green (e.g., Moldavite).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to dull.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth, often sculpted, pitted, or grooved surfaces due to atmospheric ablation. Can have flow lines or internal bubbles.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Amorphous; no crystal structure. Shapes are often aerodynamic (spheres, teardrops, dumbbells, buttons, discs) or irregular.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None, as it is an amorphous glass.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in strewn fields, which are geographically extensive areas where tektites from a single impact event are distributed. These fields are typically associated with sedimentary deposits, often in unconsolidated sands or gravels.

Key Facts

Hardness

5.5 - 6.5 on the Mohs scale

Specific Gravity

2.3 - 2.8 g/cm³ (typically higher than obsidian)

Crystal System

Amorphous (no crystal system)

Color

Black, dark brown, dark green; rarely yellowish-green

Luster

Vitreous to dull

Transparency

Translucent to opaque in thin sections; opaque in hand specimen

Fracture

Conchoidal (like broken glass)

Cleavage

None

Composition

Primarily SiO₂ (65-80%), with significant amounts of Al₂O₃, FeO, MgO, CaO, K₂O, and Na₂O. Low water content (<0.02 wt%).

Physical characteristics

• Crystal Habit: Amorphous, typically forming aerodynamic shapes (spheres, teardrops, dumbbells, buttons, discs) or irregular fragments.
• Cleavage Type: None
• Fracture Type: Conchoidal
• Tenacity: Brittle
• Luster Type: Vitreous (glassy) to dull

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