Keshi Pearls | Gemopedia

A happy accident of pearl farming, keshi pearls are produced by chance. Saltwater oysters sometimes reject their bead implant, but particles of the accompanying mantle tissue remain and stimulate the production of nacre in flat, petal-like shapes. They are often removed as seed pearls, inspiring their name, meaning "poppy seed" in Japanese. While some people think they should be considered natural pearls, they are a by-product of the culturing process so this is not technically correct. One of the most striking characteristics of South Sea keshi pearls is their very intense luster and iridescence, sometimes greater than seen in the finest cultured pearls.
Alternate
Names
Chance Pearls
Colors
Almost Any Color Usually White, Cream

Keshi Pearls Classification

Common Name

Keshi Pearls

Species

NA

Variety

Keshi Pearls

Colors

Almost Any Color Usually White, Cream

Alternate Names

Chance Pearls

Gemstone Groups

Key Separations

Appearance, RI, birefringence blink 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.

Comments

Keshi pearls are usually off round or baroque because they were formed from the mantle tissue from a rejected implantation. They are becoming rare in the market due to improved culturing techniques. Keshi pearls can be freshwater SG: 2.66 to 2.78 or Saltwater SG: 2.61 to 2.85.

Keshi Pearls 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:
LWUV:

CCF Reaction

Pleochroism

None

Dispersion

Comments

Keshi Pearls Chemistry & Crystallography

Chemical Name

calcium carbonate + conchiolin and water

Chemical Formula

CaCO3

Synthesis

Crystal System

Orthorhombic

Classification

Organic

Nature

Cultured

Crystallinity

Comments

Keshi Pearls Characteristic Physical Properties

Hardness

2.5-4

Streak

Specific Gravity

2.61-2.85

Toughness

Good

Inclusions

Keshi pearls have intense luster and iridescent surface.

Luster

Dull

Stability

Fair

Fracture

Uneven

Cleavage

None

Comments

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