Natural Saltwater Pearl | Gemopedia

Natural saltwater pearls occur in saltwater oysters without the intervention of humans. These pearls are beautiful accidents of nature caused by an irritant that becomes lodged inside the oyster. The animal naturally coats the irritant with nacre to protect its sensitive internal tissues, creating a pearl. Natural pearls are rare and are usually found by fishermen harvesting the oyster.
Colors
White, Cream, Golden, Silver, Gray, Brown, Black

Natural Saltwater Pearl Classification

Common Name

Natural Saltwater Pearl

Species

NA

Variety

Natural Saltwater Pearl

Colors

White, Cream, Golden, Silver, Gray, Brown, Black

Alternate Names

Gemstone Groups

Key Separations

refractive index, birefringence blink, specific gravity and magnification. A "tooth test" is commonly used in which a pearl is rubbed against a tooth; if gritty, this is an indication that the surface is nacre, versus plastic and glass imitations that feel smooth. X-rays are the only nondestructive test to confirm natural versus cultured origin.

Comments

Natural Saltwater Pearl Optical Properties

Transparency

Translucent - Opaque

Refractive Index

1.53-1.685

Birefringence

0.155

Optic Character

NA

Optic Sign

NA

Polariscope Reaction

Aggregate (AGG)

Fluorescence

SWUV: Variable
LWUV: Variable

CCF Reaction

Pleochroism

None

Dispersion

Comments

Natural Saltwater Pearl Chemistry & Crystallography

Chemical Name

calcium carbonate + conchiolin and water

Chemical Formula

CaCO3

Synthesis

Crystal System

NA

Classification

Organic

Nature

Natural

Crystallinity

Aggregate

Comments

Natural Saltwater Pearl Characteristic Physical Properties

Hardness

3.5-4

Streak

Specific Gravity

2.61-2.85

Toughness

Fair

Inclusions

Natural freshwater pearls will have an iridescent surface. If the pearl is drilled you can inspect the hole to look for lack of bead nucleus.

Luster

Pearly

Stability

Poor

Fracture

Uneven

Cleavage

None

Comments

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