How to identify Fossilized Shark Tooth

To correctly identify Fossilized Shark Tooth (Chondrichthyes 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, depending on the mineral composition of the surrounding sediment and the permineralization process. Common colors include black, gray, brown, tan, blue, green, and reddish-brown. The enameloid crown is often darker and shinier than the root.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to sub-vitreous on the enameloid crown, dull to earthy on the root.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth and hard on the enameloid crown, often slightly rougher or porous on the root. Serrations or cusps may be present along the cutting edges, depending on the species.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Not a true crystal, but a biogenic structure. The overall shape is characteristic of a shark tooth, with a distinct crown and root. Shapes vary from triangular, lanceolate, or bladed to flattened or pavement-like.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None, as it is a biogenic structure, not a mineral with a defined crystal lattice.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Marine sedimentary environments, particularly shallow marine shelf deposits, estuaries, and ancient riverbeds that once flowed into marine settings. Often found in unconsolidated sands, gravels, clays, and limestones.

Key Facts

Hardness

5-6 on Mohs scale (due to permineralization, primarily silica or phosphate minerals)

Specific Gravity

2.5-3.0 (variable depending on permineralizing minerals)

Crystal System

Amorphous (biogenic structure, not a true crystal)

Color

Highly variable, often black, gray, brown, tan, blue, green, or reddish-brown.

Luster

Vitreous to sub-vitreous on the enameloid, dull to earthy on the root.

Transparency

Opaque

Fracture

Conchoidal to irregular, depending on the permineralizing material and original tooth structure.

Cleavage

None

Composition

Primarily calcium phosphate (original tooth material) replaced by or infused with silica (SiO2), calcite (CaCO3), or other phosphate minerals (e.g., francolite).

Physical characteristics

• Crystal Habit: Not applicable (biogenic structure)
• Cleavage Type: None
• Fracture Type: Conchoidal to irregular
• Tenacity: Brittle
• Luster Type: Vitreous to dull

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