How to identify Fossilized Tooth

To correctly identify Fossilized Tooth (Fossil), 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

   Highly variable, often black, dark brown, gray, tan, or reddish, depending on the mineral content of the surrounding sediment during fossilization (e.g., iron oxides for red/brown, organic matter for black).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Dull to vitreous (glassy) on enamel surfaces, often earthy on broken or weathered surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth and hard on enamel surfaces, sometimes porous or granular on root sections. May exhibit fine striations or growth lines characteristic of the original tooth.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Not a true crystal form in the mineralogical sense, but retains the macroscopic morphology of the original tooth (e.g., conical, serrated, multi-cusped). Microscopic examination may reveal permineralized hydroxyapatite or replacement minerals.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None, as it is a biogenic material that has undergone permineralization or replacement, not a single mineral crystal.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in sedimentary rock formations, particularly marine deposits (e.g., ancient seabeds, coastal plains) for shark teeth, and fluvial (river) or lacustrine (lake) deposits for terrestrial animal teeth. Often associated with sandstones, limestones, shales, and phosphate beds.

Key Facts

Hardness

Variable, typically 5-7 on the Mohs scale, depending on the degree of permineralization and the replacing mineral. Original enamel is ~5, dentin ~4. Fossilization can increase hardness if replaced by silica.

Specific Gravity

Variable, typically 2.5-3.2, depending on the degree of permineralization and the replacing mineral. Original tooth material is ~2.9-3.0.

Crystal System

Not applicable (biogenic material, not a single mineral crystal). The primary mineral component, hydroxyapatite, is hexagonal.

Color

Black, dark brown, gray, tan, reddish, or mottled.

Luster

Dull to vitreous.

Transparency

Opaque.

Fracture

Conchoidal to irregular, depending on the degree of mineralization and replacement.

Cleavage

None.

Composition

Primarily calcium phosphate (hydroxyapatite) that has been permineralized or replaced by other minerals such as silica (SiO2), calcite (CaCO3), or iron oxides (e.g., Fe2O3, FeO(OH)). The original organic components are typically absent.

Physical characteristics

• Crystal Habit: Not applicable; retains the original biological morphology of the tooth.
• Cleavage Type: None.
• Fracture Type: Conchoidal to irregular.
• Tenacity: Brittle.
• Luster Type: Dull to vitreous.

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