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Demantoid

Garnet

By Tim Matthews, JD, FGA, GG, DGA,
CEO and President of JTV (retired)
Published: June 2014
Modified: September 2023
Demantoid Polished Demantoid Rough Demantoid Jewelry
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Table of Contents
  • General Information
  • Demantoid Colors
  • Demantoid Spectra
  • Countries of Origin
  • History
  • Care
  • More About Demantoid
  • Optical Phenomena

Demantoid is a rare, attractive yellowish green to intense rich emerald green variety of andradite garnet. The rich green color is due to trace amounts of chromium. Demantoid gets its name from the German word demant that translates to diamond. This is an allusion to its diamond like luster. Demantoid was discovered in Russia in 1868 during the reign of Alexander II. It was held in high regard by the Russian royal family and was the gemstone of choice for many Fabergé creations. Fibrous, wispy inclusions of byssolite or chrysotile known as horsetail inclusions are prized in demantoid garnets.

General Information

  • Classification
  • Optical Properties
  • Characteristic Physical Properties
  • Chemistry & Crystallography
Common Name
Demantoid
Species
Garnet
Transparency
Transparent - Opaque
Dispersion
Strength: Strong Fire Value: 0.057
Refractive Index
Over The Limit 1.870-1.890
Optic Character
NA
Optic Sign
NA
Polariscope Reaction
Singly Refractive (SR) With ADR
Fluorescence
SWUV: Inert
LWUV: Inert
CCF Reaction
May appear reddish
Pleochroism
None
Hardness
6.5-7
Streak
White or none
Specific Gravity
3.810-3.890 Range:0.03/-0.03 Typical:3.840
Toughness
Poor
Inclusions
Demantoid garnet is a type II clarity stone. Stones might show surface abrasions. Some stones might contain fibrous chysotile asbestos or "horsetail inclusions". Namibian stones might show stress fractures.
Luster
SubAdamantine, Vitreous
Stability
Good
Fracture
Conchoidal, Uneven
Cleavage
None
Chemical Name
calcium iron silicate
Chemical Formula
Ca3Fe2(SiO4)3
Crystal System
Cubic
Chemistry Classification
Silicate

Demantoid Colors

  • Green Demantoid
    Green
  • Green Demantoid
    Green

Demantoid Spectra

Demantoid Spectra
DEMANTOID GARNET

Color due to chromium and iron. Absorption of the blue up to 460nm masking the more typical 443nm line. Fine lines in red at 620nm, 632nm,693nm and 700nm are very difficult to detect. This is due to the high chromium content in this stone

We acknowledge the significant scientific contributions of John S Harris, FGA to the study of gemstone spectra and with deep appreciation to him, acknowledges the use of his images and related notes about gemstones and their spectra in the educational materials on this website.

Countries of Origin

Afghanistan; Russian Federation; United States of America; Madagascar; Pakistan; Unknown; China; Slovakia; France; Nigeria; Argentina; Iran (Islamic Republic of); Sri Lanka; Japan; Kenya; Switzerland; Spain; Canada; Turkey; Namibia; Congo (the Democratic Republic of the); Italy; Mexico; Germany; Tajikistan

History

In the gemstone universe there are many desirable, beautiful stones. Demantoid is one that stands with the best and the brightest. First, it is extremely rare because it is a color variety of the andradite garnet. Let's start with its green... delicious, deep-lime shades with golden-yellow flashes. The range goes from the most intense to more moderate shades. Wherever your stone lands in depth of shading, it will still hold the essence of that incomparable green, for which it can thank chromium. Demantoid is also revered for its diamond-like sheen, in fact, its name comes from the German "demant" meaning diamond-like. Well-cut demantoid has superior sparkle and fire, which makes it a very satisfying gem to own and wear. The rarest, and therefore most expensive, of all demantoids have a golden, whip-like inclusion called a horsetail. Most frequently seen in Russian stones, horsetails have been present in stones from Italy and Iran as well. This gem was originally mined in Russia around the mid-19th century before mining ceased at the time of the 1917 Russian Revolution. We are delighted that independent miners are discovering stream-worn demantoids in several areas around Ekaterinburg today. Slowly, these newly found stones are finding their way into the marketplace.

Care

Normal Care

Demantoid Gemstone

More About Demantoid

Once revered as the Czar of the garnet family, the demantoid has many historical ties to the court of Nicolas II of Russia. Demantoid's regal past includes the works of Karl Fabergé. Perhaps the lush green of the demantoid accounts for the historical belief that it could boost vitality

Optical Phenomena

Cat's-Eye

The term cat's eye, or chatoyancy, is used to describe a phenomenal optical property in gemstones, in this case demantoid garnet. The effect, when present, appears as a bright, narrow slit like the pupils in the eyes of your favorite feline. This phenomenon is caused by parallel fibrous or needle-like inclusions that interfere with the passage of light throughout the crystal, scattering and reflecting light back to the viewer as a thin line. Demantoid garnets that feature a cat's eye are rare.

  • Classification
  • Characteristic Physical properties
Common Name
Cat's-Eye
Specific Gravity
3.81
Inclusions
Chatoyancy is caused by parallel needles. Due to the stones low mohs hardness it might have scratches and abrasions.
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