Prehnite Gemstone & Information | Gemopedia by JTV | Gemopedia™

Prehnite

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 mother-of-pearl 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.

Colors

Light Green To Yellowish Green, Gray, Rarely White

  • Prehnite classification

    CommonName
    Prehnite
    Species
    Prehnite
    Variety
    Colors
    Light Green To Yellowish Green, Gray, Rarely White
    AlternateNames
    GemstoneGroups
    KeySeparations
    RI, birefringence, and spectrum. Might have to use birefringence blink method.
    ClassificationComments
  • Prehnite chemistry & crystallography

    ChemicalName
    calcium aluminum silicate hydroxide
    ChemicalFormula
    Ca2Al2Si3O10(OH)2
    Synthesis
    CrystalSystem
    Orthorhombic
    ChemistryClassification
    Silicate
    Nature
    Natural
    Crystallinity
    Crystalline to Aggregate
    ChemistryComments
  • Prehnite optical properties

    Transparency
    Translucent
    Dispersion
    OpticalComments
    RefractiveIndex
    1.616-1.649
    Birefringence
    0.02-0.033
    OpticCharacter
    Biaxial
    OpticSign
    Positive
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Inert
    LWUV: Inert
    CCFReaction
    Pleochroism
    Unobservable
  • Prehnite characteristic physical properties

    Hardness
    6-6.5
    CharacteristicComments
    Streak
    White
    SpecificGravity
    2.8-2.95 Typical:2.9
    Toughness
    Varies
    Inclusions
    Prehnite can contain epidote and copper inclusions.
    Luster
    Vitreous
    Stability
    Good
    Fracture
    Conchoidal, Uneven
    Cleavage
    Good, in one direction, Poor, in one direction