Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
Tektites are amorphous, silica-rich natural glasses, typically black, dark brown, or dark green. They are characterized by their distinctive shapes, which can be spherical, teardrop, dumbbell, button, or irregular, often with sculpted or pitted surfaces. Their formation is directly linked to large meteorite impacts on Earth's surface, making them unique among natural glasses.
How to Identify
- Color
- Typically black, dark brown, or dark green. Rarely yellowish-green (e.g., Moldavite).
- Luster
- Vitreous (glassy) to dull.
- Texture
- Smooth, often sculpted, pitted, or grooved surfaces due to atmospheric ablation. Can have flow lines or internal bubbles.
- Crystal Form
- Amorphous; no crystal structure. Shapes are often aerodynamic (spheres, teardrops, dumbbells, buttons, discs) or irregular.
- Cleavage
- None, as it is an amorphous glass.
- Geological Environment
- 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%).
Quick Check
- Color: Black, dark brown, dark green
- Luster: Vitreous (glassy)
- Streak: None (as it is glass)
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
Formation
Tektites are natural glass objects formed from terrestrial material ejected during hypervelocity meteorite impacts. The extreme heat and pressure of the impact melt the target rock, which is then launched into the atmosphere. As the molten material travels through the air, it cools and solidifies, often acquiring aerodynamic shapes due to ablation and rotation.
Usage
Historically, tektites have been used by indigenous cultures for tools, amulets, and ceremonial objects. In modern times, they are primarily of scientific interest for studying impact events and Earth's geological history. They are also collected by mineral and meteorite enthusiasts.
Age Distribution
Ranges from approximately 0.78 million years (Australasian strewn field) to 35 million years (North American strewn field) and 14.7 million years (Central European strewn field).
Where to Find
Australasian Strewn Field
Covers Southeast Asia, Australia, and Antarctica. Source of Indochinites, Philippinites, Australites, and Billitonites. Age: ~0.78 million years.
Central European Strewn Field
Primarily Czech Republic (Bohemia and Moravia) and Germany. Source of Moldavites. Age: ~14.7 million years.
North American Strewn Field
Southeastern United States (Georgia, Texas, Martha's Vineyard) and the Caribbean Sea. Source of Georgiaites and Bediasites. Age: ~35 million years.
Ivory Coast Strewn Field
West Africa (Ivory Coast, Ghana). Source of Ivorites. Age: ~1.07 million years.
Finding Tips
Strewn Field Knowledge
Focus your search within known tektite strewn fields. Each field has distinct tektite types and ages.
Surface Collection
Tektites are often found on the surface in areas of erosion or in shallow alluvial deposits, particularly after rain or disturbance of the soil.
Distinguishing from Terrestrial Rocks
Look for the characteristic glassy texture, lack of crystal structure, and often aerodynamic shapes. Tektites are typically denser than common terrestrial rocks of similar size.
Magnetism Test
While not magnetic themselves, some tektites may contain tiny inclusions of nickel-iron spherules from the impactor, which can be detected with a strong magnet. However, this is not a primary identification method.
Similar Rocks
Obsidian
Obsidian
Also known as: Volcanic Glass
Impact Glass
Impact Glass
Also known as: Impact Melt Glass
Fulgarite
Fulgarite
Also known as: Fossilized Lightning
Scientific Classification
- Mineral Class
- Not a mineral (amorphous)
- Group
- Natural Glass / Impactite
- Crystal System
- Amorphous
- Chemical Formula
- Variable, primarily SiO₂ with other oxides (e.g., Al₂O₃, FeO, MgO, CaO, K₂O, Na₂O)
- Composition
- Silica-rich natural glass, formed from melted terrestrial rock during meteorite impacts.
Explore Tektite
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.