aLEXANDRITE

Natural alexandrite and diamond station necklace, in platinum, by Global Gemology

Variety:  Alexandrite
Species:  Chrysoberyl
​​Mohs Hardness:  8.5 out of 10
Color:  Bluish green to green in fluorescent light, purplish red to red in incandescent light.
RI:  1.746 to 1.755 (+0.004 / -0.006)
Phenomena:  Color change
Birefringence:  0.008 to 0.010
SR/DR/AGG:  DR
Clarity Type:  Type II
Optic Character:  Biaxial positive
Pleochroism:  Strong green, orange & purple-red trichroism
Spectrum:  Purple/Red direction:  Strong lines in the red at 678 & 680.5nm.  Weaker ones at 645 & 655nm.  Broad absorption from 540 to 605nm.  Green direction:  Strong lines in the red at 678 & 680.5nm.  Weaker ones at 645, 649, 655 & 665nm.  Broad absorption from 555 to 640nm.
Fluorescence:  Inert to moderate red under LW & SW.
SG:  3.73 (+/-0.02)
Routine Treatments:  None

alexandrite Facts

A natural alexandrite and diamond engagement ring.

Alexandrite is a variety of chrysoberyl that possesses a rare phenomenon known as color change.

Alexandrite is often referred to as "emerald by day, ruby by night", as it appears greenish in daylight and red/purple in lamplight.

Natural alexandrite is very rare and can be quite expensive depending on size and quality.

​Alexandrite was originally discovered in Russia's Ural Mountains in the 1830s and was named after the Russian tsar, Alexander II.  Alexandrite is now found in Sri Lanka, East Africa and Brazil.

Alexandrite is a June birthstone and is the 55th wedding anniversary gemstone.

Natural alexandrite in daylight vs. incandescent light

Lab Created alexandrite

Photo courtesy of JTV

Lab created (synthetic) alexandrite is seen much more frequently than natural alexandrite, due to the rarity and cost of the natural variety.

Lab created alexandrite is produced by either the flux method or the floating zone method.

Photos courtesy of Scott Papper, GIA GG, AJP, CMA (NAJA) unless otherwise mentioned.

Lab Created alexandrite