Difference between revisions of "Beryl"

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Pleochroism: weak to moderate, strong in "True Blue" Aquamarine and Pezzottaite.
 
Pleochroism: weak to moderate, strong in "True Blue" Aquamarine and Pezzottaite.
  
===Diapheny===
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===Diaphanity===
  
 
Transparent to opaque.
 
Transparent to opaque.

Revision as of 11:50, 25 October 2006

Beryl
Chemical composition Be3Al2(SiO3)6 Beryllium aluminum silicate
Crystal system Hexagonal
Habit Prismatic
Cleavage Very difficult in one direction, rarely seen
Fracture Conchoidal
Hardness 7.25-7.75
Optic nature Uniaxial -
Refractive index 1.577-1.583
(+ or - 0.017)
Birefringence 0.005-0.009
Dispersion Low, 0.014
Specific gravity 2.72
(+0.18,- 0.05)
Lustre Vitreous to resinous
Pleochroism Weak to moderate

Beryl is a beryllium aluminum silicate that occurs in every color of the rainbow. When green, it's an emerald. When blue, it's aquamarine. When pink, it's morganite. There is a raspberry red variety found in Utah called Bixbite. Yellow is heliodor and colorless is goshenite. There is a very rare and costly variety termed riesling beryl, that can be described as pale green colour, with a warm golden yellow flash. Two unusually dark blue types of beryl have been found as well, Maxixe beryl and True Blue beryl. Maxixe beryl fades with exposure to light, True Blue beryl does not. Beryl had been used as a physician's tool and gazing stone since ancient times. Those beliefs persist today. Beryl is metaphysically attributed with the ability to cure a number of intestinal and stomach ills, such as nausea, ulcers, and seasickness.


Characteristics

The optical and physical data of Beryl can vary between varieties and localities.
Beryl belongs to the Beryl Group (another member of the Beryl Group is Pezzottaite).

Genesis

Metamorphic rocks in pegmatites

Localities

Beryl is found in many localities, amongst them are Brazil, India, Africa, Columbia, Australia and Pakistan.

Habit

Prismatic with pyramidal and/or pinacoidal terminations. Often vertically striated.

Physical data

Moh's hardness: 7.25 - 7.75 (Emerald is brittle).
Specific gravity: 2.7 to 2.9, depending on variety.

Optical data

Refractive index: nε = 1.56 nω = 1.59, depending on variety.
Birefringence: 0.004 to 0.009, depending on variety.
Optical sign: uniaxial negative.
Dispersion: low, 0.014
Pleochroism: weak to moderate, strong in "True Blue" Aquamarine and Pezzottaite.

Diaphanity

Transparent to opaque.

Colors

Beryl and all its varieties are allochromatic. Main coloring agents are given.

  • Green (Emerald), colored by Chromium 3+
  • Green (Vanadium Beryl), colored by Vanadium 3+ - Also known as Vanadium Emerald
  • Green (Green Beryl), colored by Ferric 3+ and ferrous 2+ Iron
  • Green/Yellow (Reisling Beryl), unknown coloring agent (most likely Iron)
  • Blue (Aquamarine), colored by Ferrous 2+ Iron
  • Blue (Maxixe), colored by color centers
  • Blue (True Blue), colored by Ferrous 2+ Iron - Tradename for high FeO content Aquamarine
  • Pink (Morganite), colored by Manganese 2+
  • Red (Bixbite), colored by Manganese 3+
  • Yellow (Heliodor), colored by Ferric 3+ Iron
  • Colorless (Goshenite)