Alexandrite

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Alexandrite is the rare color-change variety of the mineral chrysoberyl. Its rarity is a result of its unlikely chemical makeup. Alexandrite can only form when aluminum and beryllium combine with trace elements like iron, titanium and, most importantly, chromium. On rare occasion, vanadium may also be present. The unlikelihood of the rare element chromium being in the right place to combine with aluminum and beryllium under exactly the right conditions to create alexandrite is what makes it so rare and valuable.

Alexandrite Polished
Alexandrite Classification
Common Name Alexandrite
Species Chrysoberyl
Alexandrite Optical Properties
Transparency Transparent
Dispersion Strength: Weak Fire Value: 0.015
Refractive Index 1.746-1.755
Tolerance:(+0.004/-0.006)
Birefringence 0.008- 0.010
Optic Character Biaxial
Optic Sign Positive
Polariscope Reaction Doubly Refractive (DR)
Fluorescence SWUV: inert to moderate red
LWUV: inert to moderate red
CCF Reaction red
Pleochroism Trichroic, strong green, orange and purplish red
Alexandrite Characteristic Physical Properties
Hardness 8.5
Streak White
Specific Gravity 3.710-3.750 Range:+/- 0.02
Toughness Varies
Inclusions Alexandrite is a type II clarity stone. The stone may contain fluorite, apatite, mica platlets, rutile and multi-phase inclusions along with negative crystals, fingerprints, liquid inclusions, needles and hollow tubes. Alexandrite's might show twinning.
Luster Bright Vitreous
Stability Very Good
Fracture Conchoidal
Cleavage Good, in one direction
Alexandrite Chemistry & Crystallography
Chemical Name beryllium aluminum oxide
Chemical Formula BeAl2O4
Crystal System Orthorhombic
Chemistry Classification Oxide

Alexandrite Colors

  • Brown Alexandrite Brown
  • Green Alexandrite Green
  • Purple Alexandrite Purple
  • Red Alexandrite Red
  • Yellow Alexandrite Yellow

Countries of Origin

Tanzania, United Republic Of; Unknown; Sri Lanka; China; Russian Federation (the); Brazil; Mexico; Zimbabwe; Madagascar; Switzerland; India

History

Color-change alexandrite is a chrysoberyl and an 8 ½ on the Mohs scale of hardness. Although first found in the Ural Mountains of Russia, it is now mined in many places around the world, but its connection to Russian history is unwavering. Fine quality alexandrite is extremely rare and expensive. Alexandrite is an alternative birthstone for the month of June.

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More About Alexandrite

According to legend, alexandrite was discovered on the 16th birthday of the young man who would become Tsar Alexander II. In truth, it was discovered before that day. The stone, however, still bears his name. Many cultures believe that alexandrite brings good omens, change and renewal. To the Russian people in the later 1800s, it was thought to be a stone of prophecy and good fortune.

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Creation Classification

Lab Created

Some gems, like alexandrite, are almost impossible to find in nature today, much less in the sizes and quality people dream of owning.Synthetic alexandrite can be created in a variety of ways including flux growth, Czochralski method, or floating zone method.Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.

Lab Created Alexandrite
Lab Created Classification
Common Name Lab Created
Lab Created Optical Properties
Fluorescence SWUV: Moderate to strong red
LWUV: Moderate to strong red
CCF Reaction NA
Lab Created Characteristic Physical properties
Inclusions Flux grown synthetic alexandrite might have metallic platelets from the platinum crucible, veil like inclusions, flux inclusions, flux filled cavities, straight or angular growth lines layers of dust-like inclusions parallel to seed plate.Czochralski method pulled stones will have needle like inclusions, curved striae and small black like gas bubbles.Floating zone or hydrothermal stones will have dark gas bubbles, long flat liquid inclusion and a swirled appearance.

Optical Phenomena

Cats-Eye

The term cat's eye, or chatoyancy, is used to describe a phenomenal optical property in gemstones, in this case chrysoberyl. The effect, when present, appears as a bright, narrow slit similar to the pupils in the eyes of your favorite feline. This phenomenon is caused by parallel fibrous or needle-like inclusions that interfere with the passage of light throughout the crystal, scattering and reflecting light back to the viewer as a thin line.Chatoyant chrysoberyl is particularly incredible because it exhibits two rare phenomena: both the cat's eye effect and color change.

Cats-Eye Alexandrite
Cats-Eye Classification
Common Name Cats-Eye
Cats-Eye Characteristic Physical properties
Inclusions Natural cat's-eye alexandrite typically has fine needles or hollow tubes. The stones can have fluorite, apatite, mica platlets, rutile and multi-phase inclusions along with negative crystals, liquid and fingerprint inclusions. Some stones might show twinning.
Tim Matthews

Author

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.