Tridacna Pearls | Gemopedia

Tridacna pearls form within the tridacna clam, commonly known as the "giant clam." These large mollusks grow in the warm coral reefs of the Indo-Pacific Ocean, living up to 100 years and reaching sizes of up to 47 inches across. Understandably, the largest pearl of any kind on record is a tridacna pearl weighing 6.4 kilograms. These non-nacreous pearls have a porcelain-like white surface.
Colors
Yellowish White

Tridacna Pearls Classification

Common Name

Tridacna Pearls

Species

NA

Variety

Tridacna Pearls

Colors

Yellowish White

Alternate Names

Gemstone Groups

Key Separations

RI, birefringence blink, magnification and appearance.

Comments

Use birefringence blink method to obtain birefringence. Tridacna pearls are not a true pearls, they come from the giant clam. They range in size from 1 cm to very large. Misnomer: coconut pearl.

Tridacna Pearls Optical Properties

Transparency

Translucent To Opaque

Refractive Index

1.53-1.685

Birefringence

0.155

Optic Character

Optic Sign

Polariscope Reaction

Aggregate (AGG)

Fluorescence

SWUV: Variable
LWUV: Variable

CCF Reaction

Pleochroism

None

Dispersion

Comments

Tridacna Pearls Chemistry & Crystallography

Chemical Name

calcium carbonate, conchiolin and water

Chemical Formula

CaCO3 with H2O and other organic materials

Synthesis

Crystal System

NA

Classification

Carbonate

Nature

Natural

Crystallinity

Aggregate

Comments

Tridacna Pearls Characteristic Physical Properties

Hardness

2.5-4

Streak

Specific Gravity

2.83-2.87 Typical: 2.85

Toughness

Fair

Inclusions

Tridacna pearls have a yellow to white porcelain appearance with flame like structure.

Luster

Dull

Stability

Poor

Fracture

Uneven

Cleavage

None

Comments

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