ALEXANDRITE

Alexandrite is the color-change variety of the mineral species chrysoberyl, and is the one of the birthstones for June.

The most sought after alexandrites are a lovely green in daylight or fluorescent light, but change to red or slightly purplish red in the incandescent light from a lamp or candle flame.

Abundant alexandrite deposits were first discovered in 1830, in Russia's Ural Mountains. Those first alexandrites were of very fine quality, and displayed vivid hues and dramatic color changes. The gem was named after the young Czar Alexander II, and it caught the country’s attention because its red and green colors mirrored the Imperial Russian flag.

The spectacular Ural Mountain deposits didn’t last forever, and now most alexandrite comes from Sri Lanka, Brazil, India, Tanzania, and Madagascar. The newer deposits contain some fine-quality stones, but many possess less precise color change and muddier hues than the 19th century Russian alexandrites. You may still find some of the famed Ural Mountain alexandrites in estate jewelry. They remain the quality standard for this phenomenal gemstone.

Gemology
Alexandrite has a hardness of 8.5 on the Mohs hardness scale, and has excellent toughness. Alexandrites are typically transparent, and may contain fingerprint and silk inclusions.

Typical size range
Alexandrites typically come in sizes from melee to 5 carats. Larger stones are rare.

Treatments
None known

Sources
Sri Lanka and Brazil are the two major producers. Alexandrite is also found in Madagascar, Tanzania, India, Sri Lanka, and Russia.

Care and Cleaning
Alexandrite can be cleaned in warm, soapy water. Ultrasonic cleaning and steam cleaning are usually safe.

Simulants, synthetics, and alternatives
Synthetic alexandrite was developed in 1973. It can be grown using the flux or Czochralski methods. Synthetic alexandrite will have a similar color change to natural alexandrite, bluish green in daylight and brownish red to purple-red in incandescent light. Synthetic alexandrites often have flux inclusions, triangular metallic platelets, curved striae, or gas bubbles, depending on the growth technique that was used to grow the synthetic. Synthetic alexandrites typically have a slightly lower RI, and stronger fluorescence than natural alexandrites.
Synthetic color-change corundum (of which ruby and sapphire are varieties) was developed approximately in 1909. The color change in alexandrite-like synthetic sapphire will be bluish purple or greenish blue changing to reddish purple, depending on the growth process used to create the synthetics.
Synthetic color-change spinel.

Color-change garnet
Color-change sapphire