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Beryl Education

 


GENERAL DESCRIPTION

 

  • Name: Beryl is derived from the Prakrit word veruliyam, which developed into berullus in Latin and beryllos in Greek.
    1. Formula: Be3 Al2 (Si6 O18)
    2. Crystal system: hexagonal.
    3. Habit: Prismatic.
    4. Cyclosilicates Six-Membered Rings with [Si6O18] rings; possible (OH) and Al substitution.
    5. Common Impurities:  Fe, Mn, Mg, Ca, Cr, Na, Li, Cs, O, H, OH, H2O, K, Rb
      • Emerald : Chrome and / or Vanadium
      • Heliodor : Iron 
      • Aquamarine: Iron
      • Maxixe: Iron or color centers
      • Morganite : Manganese
      • Red Beryl : Manganese
    6. Genesis: Pegmatite - Hydrothermal pneumatolytique, Metamorphic.  Commonly found in pegmatites.
    7. Origen: Beryl is found:
      • Emerald : Colombia, Brazil, Russia, Pakistan, South Africa, Zambia, Zimbabwe, etc. .       
      • Heliodor : US, Brazil, Argentina, Namibia, Pakistan, etc.
      • Aquamarine: Brazil, Madagascar, Mozambique, Colorado, Russia, Norway, Pakistan, Myanmar, etc.
      • Maxixe: Brazil
      • Morganite : Brazil, Namibia, Zimbabwe, Madagascar, Mozambique, US, Canada, Russia, Pakistan, Afghanistan, etc.
      • Red Beryl : US (New Mexico).

     

    Biphasic Inclusion in Morganite

     

    Triphasic Inclusion in Goshenite

     

    Hollow tubes in Aquamarine 

    PHYSICAL AND OPTICAL PROPERTIES OF BERYL

     

    • Hardness (Mohs): 7½ – 8
    • Fracture: Conchoidal.
    • Colour: Light green to dark green (Emerald), light blue to blue (Aquamarine), yellow to orange yellow Dark (Heliodor),  Electric Blue (Maxixe), Colorless (Goshenite), red (Red Beryl), pale pink (Morganite), green apple (Green Beryl), sometimes asterism or chatoyancy.
    • Transparency: Transparent, translucent, opaque.
    • Streak: White.
    • Lustre: Vitreous, sub-vitreous, waxy, greasy.
    • Dispersion: 0,014 Low.
    • Density: 2.60 – 2.90 g/cm3
    • Optic nature: Uniaxial -
    • Refractive index:  nω.=1,560-1,602 y nε=1,566-1,59
      • Emerald: 1,565 – 1,571 a 1,588 – 1,595
      • Heliodor: 1,570 – 1,575 (±0,004)
      • Aquamarine: 1,575 – 1,580 (±0,005)
      • Morganite: 1,585 – 1,594 (±0,006).
    • Birefringence: δ  0,006 (0,004 – 0,009).
    • Pleochroism: Weak to moderate.
    • Fluorescence: Variable. Commonly no observable.
      • Emerald: no observable to red (Short UV: low – red to orange; Long UV: more intense – Green to dark red, and sometimes, intense red in synthetic emeralds).
      • Morganite: Null to low: lilac, violet
    • Phosphorescence: Null.
    • Absorption spectrum:  Variable: from no observable to observable
      • Emerald: Chrome. Natural and synthetic Emerald have a similar spectra with a little variation.
      • Red Beryl: Manganese. Difficult to see.
      • Aquamarine: Difficult to see. Iron.
      • Maxixe: Iron. Sometimes observable (null if heated stone).
    • Inclusions: Channels, hollow tubes, negative crystals, biphasic and triphasic inclusions, pyrite crystals, calcite crystals, dolomite, albite, mica plates, etc.
    • Enhancements:
      • Emerald: Common enhancements: fracture filling (oil, wax, plastic, or chemical compounds). The majority of emeralds have treated.
      • The beryls are almost always heat-treated. And most aquamarine is treated (heated 400-450º C) to reduce Fe3+ (heat drives off the yellow or green tinge, leaving a purer blue). Morganite is heat-treated. The resulting color is stable and won’t fade, and does not affect the value.

     

    Growth tubes, (parallel channels) in Heliodor. 

     

    Solid Inclusion in Aquamarine

     

    Gas-liquid' and solid, 'growth tubes giving the cat eye effect' in Aquamarine

     

     Liquid filled inclusions; fingerprint inclusions in Morganite

     

    Fracture in Morganite