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Kasumiga Pearl

Pearl

By Tim Matthews, JD, FGA, GG, DGA,
CEO and President of JTV (retired)
Published: June 2014
Modified: September 2023
Kasumiga Pearl Polished
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Table of Contents
  • General Information
  • Kasumiga Pearl Colors
  • Alternate Names
  • Countries of Origin
  • History
  • Care

Japan’s Lake Biwa once produced freshwater pearls were very popular among freshwater pearl lovers, but ongoing pollution issues led to their extinction in recent decades. To fill the void left in the market, Japanese pearl growers began culturing freshwater pearls in Lake Kasumigaura, located in northeastern Japan. Kasumigaura’s name translates to “the body of water beyond the mist” and the pearl farms are located in the upstream areas. Unfortunately, these pearls have also become increasingly scarce due to environmental issues. While there are reports that Kasumiga pearl production ceased in 2006-2007, production continues, on a very, very small scale. Kasumiga pearls are grown by using a bead-nucleated hybrid mussel and are known (and highly prized) for their large sizes and high luster. Good quality Kasumiga pearls rival the value and rarity of South Sea pearls. They are just as large and lustrous with a variety of colors ranging from white, cream, pink to purple. The size of the pearls can range from 9 – 13mm. Because of the ongoing environmental issues, finer quality Kasumiga pearls are extremely limited—and highly desirable to pearl lovers around the world. Because of their rarity, Kasumiga pearls can command premium prices for the finest qualities.

General Information

  • Classification
  • Optical Properties
  • Characteristic Physical Properties
  • Chemistry & Crystallography
Common Name
Kasumiga Pearl
Species
Pearl
Transparency
Opaque-Translucent
Dispersion
Strength: None
Refractive Index
1.530-1.685
Birefringence
0.155
Optic Character
NA
Optic Sign
NA
Polariscope Reaction
Aggregate (AGG)
Fluorescence
SWUV: Cream/light yellow: inert to very weak green; Cream: inert; Pink/purple/golden extremely weak chalky green or bluish green; Orange: inert
LWUV: Cream/light yellow: weak chalky green blue; Cream: blue; Pink/purple/golden Inert to very weak chalky green or bluish green; Orange: inert
Pleochroism
None
Streak
White
Toughness
Good
Inclusions
Sometimes they will show black or brown blemishes that are remnants of organic matter. You might see aragonite platelets under magnification.
Luster
Pearly
Stability
Fair
Fracture
Uneven
Cleavage
None
Chemical Name
calcium carbonate + conchiolin and water
Chemical Formula
CaCO3
Crystal System
NA
Chemistry Classification
Organic

Kasumiga Pearl Colors

  • Blue Kasumiga Pearl
    Blue
  • Brown Kasumiga Pearl
    Brown
  • Gray Kasumiga Pearl
    Gray
  • Orange Kasumiga Pearl
    Orange
  • Pink Kasumiga Pearl
    Pink
  • Purple Kasumiga Pearl
    Purple
  • Yellow Kasumiga Pearl
    Yellow

Alternate Names

Kasumi Pearls, Japanese Cultured Freshwater Pearl

Countries of Origin

Unknown; Japan

History

Lake Kasumigaura is Japan’s second largest lake. Pearl farming was first initiated at the lake in 1931 but it did not gain prominence until the 1980’s when pearl farming at Lake Biwa began to decline. The oysters that are used for pearl farming are hybrids of the Hyriopsis schlegelii and Hyriopsis cumingii oysters. All the pearls are bead nucleated and the growth period is between 3.5 to 4 years.

Care

Avoid cosmetics, perfumes, hairsprays, heat and household chemicals. Pink Kasumiga pearls will fade if exposed to heat.

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