Tortoise Shell

Ornamental tortoise shell is obtained from the carapace or shield of the hawksbill turtle found in the Malay Archipelago, West Indies and Brazil. The colour is mottled and mainly
a translucent yellow with brown mottling.
Generally thicker shells are used to make jewellery which is brown in color with white spots.

Properties

Chemical Composition: Complex Protein (keratin)

Classification / Type: Obtained from the carapace of a sea turtle.

Colors / Varieties: Mottled yellow and brown.
Transparency: Translucent to Opaque.

Crystal System / Forms: None. Amorphous.

Hardness: 2.5

Specific Gravity: 1.29

Cleavage / Fracture: None / Uneven.

Optic Character: A.G.G.

Lustre: Oily to waxy.

Refractive Index / Birefringence: 1.55 / Nil.

Pleochroism: None.

Dispersion: None.

Magnification: Mottled sections show spherical spots of color. Larger numbers of dots give rise to deeper shades of color.

U.V. Fluorescence: Yellow portions give blue white fluorescence.

Spectrum: None.

Treatment (Enhancement): Colored impregnation (dyeing)

Specific Tests & Remarks: 

• Sectile and brittle.
• Thermoplastic nature which softens in boiling water; used to produce large sheets.
• Excessive heat darkens the color.
• Burnt hair odor.

Synthesis: None.

Simulants (with key separation tests): 

• Most commonly plastic (bakelite).
• Dust and scrapings of tortoise shell are softened and moulded, also dyed to produce darker colors.
• Doublet - tortoise shell on a plastic base.

Geological Occurrence: -

Sources: Shell of turtles which are found at Indonesia, Indian Ocean, Malay Archipelago, Brazil and West Indies.

Cuts & Uses: Cabochons, used for inlay work, carvings, decorative combs and other items.