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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, pearly or 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.

Prehnite Polished
Prehnite Classification
Common Name Prehnite
Species Prehnite
Prehnite Optical Properties
Transparency Translucent-Transparent
Dispersion Strength: None
Refractive Index 1.611-1.669
Birefringence 0.02-0.033
Optic Character Biaxial
Optic Sign Positive
Polariscope Reaction Aggregate (AGG), Doubly Refractive (DR)
Fluorescence SWUV: Inert
LWUV: Inert
CCF Reaction None
Pleochroism Unobservable
Prehnite Characteristic Physical Properties
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 Good
Fracture Conchoidal, Uneven
Cleavage Good, in one direction, Poor, in one direction
Prehnite Chemistry & Crystallography
Chemical Name calcium aluminum silicate hydroxide
Chemical Formula Ca2Al2Si3O10(OH)2
Crystal System Orthorhombic
Chemistry Classification Silicate

Prehnite Colors

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

Countries of Origin

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


Normal Care, but avoid sudden temperature changes.

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Tim Matthews


Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.