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Prehnite

Prehnite

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

Prehnite is the first gemstone named for a person. It was named in honor of Colonel Hendrik Von Prehn, the Dutch mineralogist credited with its discovery in the 1700's in South Africa. Also, prehnite was the first mineral to be named and described from South Africa, long before the country became an important source for precious gems, including diamond. Many specimens of this gem have an interesting luminous quality, with a vitreous to greasy luster. With color ranging from pale green to a pale yellowish green and a hardness of 6 - 6.5, Prehnite is considered to be fairly sturdy and long wearing when set in jewelry.

General Information

  • Classification
  • Optical Properties
  • Characteristic Physical Properties
  • Chemistry & Crystallography
Common Name
Prehnite
Species
Prehnite
Transparency
Semitransparent-Translucent
Dispersion
Strength: None
Refractive Index
1.611-1.669
Birefringence
0.020- 0.033
Optic Character
Biaxial
Optic Sign
Positive
Polariscope Reaction
Aggregate (AGG), Doubly Refractive (DR)
Fluorescence
SWUV: Inert
LWUV: Inert
CCF Reaction
None
Pleochroism
Unobservable
Hardness
6-6.5
Streak
White
Specific Gravity
2.800-2.950 Typical:2.900
Toughness
Fair
Inclusions
Prehnite can contain epidote and copper inclusions.
Luster
Vitreous, Pearly, Greasy
Stability
Fair
Fracture
Conchoidal, Uneven
Cleavage
Good, in one direction, Poor, in one direction
Chemical Name
calcium aluminum silicate hydroxide
Chemical Formula
Ca2Al2Si3O10(OH)2
Crystal System
Orthorhombic
Chemistry Classification
Silicate

Prehnite Colors

  • Blue Prehnite
    Blue
  • Gray Prehnite
    Gray
  • Green Prehnite
    Green
  • Green Prehnite
    Green
  • Green Prehnite
    Green
  • Pink Prehnite
    Pink
  • White Prehnite
    White
  • Yellow Prehnite
    Yellow
  • Yellow Prehnite
    Yellow

Countries of Origin

United States of America; Madagascar; United Kingdom of Great Britain and Northern Ireland; French Polynesia; India; Canada; Austria; Pakistan; Unknown; Mali; Norway; China; Namibia; Brazil; Italy; South Africa; Israel; Australia; France; Nigeria; Germany

Care

Normal Care, but avoid sudden temperature changes.

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