Chrysoberyl / Alexanderite
Color: Chrysoberyl – Golden-yellow, greenish to brownish.
Alexandrite – Color change from green to purple or red. Moh’s hardness: 8.5 Refractive Index: 1.744-1.755
Critical Angle: 35°
Specific Gravity: 3.70-3.72
Fracture: Weak, conchoidal
Heat Sensitivity: Can be, cracks and cleavages may open up and travel with heat.
Dichroic: very weak (reddish to yellowish or yellow to pale-green)
Birefringence (double refraction): Medium (.011)
Crystal Structure: Orthorhombic
Treatments: Generally none, sometimes can be irradiated.
What I prefer to polishing with: 8,000 pre-polish 50,000 polish with Zinc laps (scored)
Jeff’s Comments: Cuts and polishes similar to Sapphire but with much less directional hardness. Watch the heat when dopping… For Alexsanderite the color change exhibited must be a strong change in color when the light source switches from daylight or fluorescent to incandescent. Many stones exhibit a shift in color, but true color change stones must exhibit a dramatic change, such as green to red or blue to red. True alexandrite is extremely rare and expensive. Beware that very good synthetic Alexandrite is currently on the market.
Design Notes: About any designs will work well… I like deep designs because the color(s) are usually on the light side
Design Links: White Asterism – This is great for clear rough if you have a piece that will work…