Conch Pearl | Gemopedia

A conch is a marine gastropod or, more simply, a large sea snail. Conchs are valued for their meat, shell and non-nacreous pearls. Conch pearls are formed by concentric layers of fibrous calcium. This layering often produces a much-desired flame structure, which is characteristic of conch pearls. Because they are a calcareous concretion, the pearls have a porcelain finish and luster, very similar to the interior of the conch shell. Conch pearls are not cultured, but are usually found as a by-product as fishermen clean their catch for conch meat. The gems are usually baroque or oval in shape and generally a salmon-colored orange-pink.
Colors
Beige, Ivory, White, Brown, Mottled Coloring Pink, Yellow, Orange, Red

Conch Pearl Classification

Common Name

Conch Pearl

Species

NA

Variety

Conch Pearl

Colors

Beige, Ivory, White, Brown, Mottled Coloring Pink, Yellow, Orange, Red

Alternate Names

Gemstone Groups

Key Separations

RI, birefringence blink, magnification and appearance

Comments

Use birefringence blink method to obtain birefringence. Misnomer: Nassau pearls. Conch pearls are not considered true pearls. They come from the giant conch Strombus gigas. Color may fade if pearl is exposed to sunlight for long periods of time.

Conch Pearl Optical Properties

Transparency

Translucent - 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

Conch Pearl 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

Non-Crystalline

Comments

Conch Pearl Characteristic Physical Properties

Hardness

2.5-4

Streak

Specific Gravity

2.83-2.87 Typical:2.85

Toughness

Fair

Inclusions

Conch pearls have a flame like structure and does not have nacre but a porcelain like finish.

Luster

Dull

Stability

Poor

Fracture

Uneven

Cleavage

None

Comments

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