How to identify Shark Tooth Fossil

To correctly identify Shark Tooth Fossil (Fossilized Chondrichthyes tooth), 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, typically black, dark brown, gray, blue-gray, or reddish-brown, depending on the mineral content of the surrounding sediment during fossilization. Rarely white or cream if found in very young, unmineralized deposits.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Dull to sub-vitreous, often earthy due to surface weathering or mineral coatings.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth to slightly granular on the enameloid crown, often rougher or porous on the root. Serrations, if present, are sharp.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Not a true crystal form, but rather a biogenic structure. The original tooth structure is preserved, consisting of a crown (enameloid) and a root (dentin).

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

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

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in marine sedimentary deposits, including sands, silts, clays, limestones, and phosphatic beds. Common in ancient shallow marine environments, river deltas, and coastal plains where marine sediments accumulated.

Key Facts

Hardness

5-6 on the Mohs scale (due to the enameloid and diagenetic mineralization)

Specific Gravity

2.5-3.0 (can vary based on mineralization and infilling)

Crystal System

Amorphous (biogenic structure, not a true mineral crystal system)

Color

Black, dark brown, gray, blue-gray, reddish-brown

Luster

Dull to sub-vitreous, earthy

Transparency

Opaque

Fracture

Conchoidal to irregular, brittle

Cleavage

None

Composition

Primarily calcium phosphate (hydroxyapatite) with varying amounts of other minerals (e.g., iron oxides, silica) replacing organic material during fossilization.

Physical characteristics

• Crystal Habit: Not applicable; biogenic structure retaining original tooth morphology (e.g., triangular, blade-like, multi-cusped).
• Cleavage Type: None
• Fracture Type: Conchoidal to irregular
• Tenacity: Brittle
• Luster Type: Dull to sub-vitreous, earthy

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