Mineral Information and Data:

Chrysoberyl
BeAl2O4 [CNMNC approved formula]

Named from the Greek χρυσός, golden, and βήρυλλος, beryl, in allusion to the color. Originally named chrysoberil(1790).

IMA status : Valid species (Pre-IMA 1790) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
07.02.09.01  
  (07) Multiple Oxides
  (07.02) (A+ B++)2 X4 Spinel group
  (07.02.09)
  
Nickel-Strunz
(10th edition) :
04.BA.05
  (04) Oxides and Hydroxides
  (04.B) Metal:Oxygen = 3:4 and similar
  (04.BA) With small and medium-sized cations
  
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Unit cell: a = 5.488 Ǻ, b = 9.423 Ǻ, c = 4.433 Ǻ
Crystal Habit: Crystals thin to thick tabular or short prismatic; granular massive
Twinning: Common on {130}, contact, penetration, or cyclic (sixlings)
  
Color: Yellowish green, yellow, grey, brown, blue-green
Diaphaneity: Transparent to translucent
Luster: Vitreous
Hardness (Mohs): 8.5
Measured Density: 3.75 g/cm3
Cleavage: 3; {110} distinct, {010} imperfect, {001} indistinct
Tenacity: Brittle
Fracture: Uneven to conchoidal
Streak: White
  
Geologic Setting: Characteristic of some granite pegmatites associated with high-grade mica schists
or reaction zones in ultramafic rocks; also detrital in placers.
Mineral Association: Quartz, muscovite, albite, beryl, columbite, tourmaline, topaz, kyanite, staurolite (granite pegmatites); phenakite, apatite, tourmaline, fluorite (reaction zone pegmatites)
  
Synonyms/varieties: Alexandrite (color-change var.), cymophane (opalescent var.)
Other Properties: Gemstone Readily Available.

 

Chrysoberyl
Origin: Lac Alaotra, Madagascar
Sample size: left twinned crystal 2 x 2 cm x 4 mm
Photo: Tom Loomis

 

Chrysoberyl
Origin: Rio das Pratinhas, Arataca, Bahia, Brazil
Sample size: 3.5 x 3 x 2 cm
Photo: Tom Loomis

 

Chrysoberyl
(zoom-in of above)

 

Chrysoberyl
Variety alexandrite
Origin: Caraiba, Pindobacu, Brazil
Sample size: 3.5 x 3.2 x 2.2 cm (2nd row)
Photo: John Veevaert, Trinity Mineral Co

 

Chrysoberyl
(zoom-in of above)

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