Natural Cat Eye Alexandrite 3.89ct

Wiki
Weight: 3.89ct
Dimensions: 8.32 x 7.49 x 6.39mm

Front nature light
alexandrite cat eye 3.89ct in nature light

Front white light
alexandrite cat eye 3.89ct in white light

Front yellow light
alexandrite cat eye 3.89ct in yellow light

Back yellow light
the back of alexandrite cat eye 3.89ct in yellow light

GRS report Large
GRS report for alexandrite cat eye 3.89ct

Formula: BeAl2O4
Mineral class: oxides
Crystal system: orthorhombic
Mohs scale: 8.5
Density (g/cm3): 3.64 - 3.68
Refractive index: 1.746 - 1.755
Colors: green (in variations) to blueish / violet in daylight, orange to reddish / violet in artificial light. The color change effect is based on traces of chromium which partially replaces the aluminium.
Transparency: transparent
Luster: vitreous
Fluorescence: red
Pleochroism / Trichroism: strong. X= red - violet, Y= orange, Z= green
Ural / Russia: profound red - yellow orange - green blue
Andhra Pradesh / India:
Sri Lanka: red - orange - green
Mogok / Myanmar: purple - grass green - green blue
Minas Gerais / Brazil: dark red - orange-yellow - green
Tunduru / Tanzania:
"Alexandrite effect": Alexandrite is a trichroic gemstone which may absorb and reflect light differently in each of its three optical directions. However, it is not the trichroism that is responsible for the remarkable change. The color change phenomena is a result of the presence of Cr3+ ions, and the way they are absorbed and reflected ... In alexandrite, where the Cr absorption band is at 580nm and right between ruby red (550nm) and green emerald (600nm), the stone is balanced between them. When the light is balanced (daylight), the stone will be green but when the light source is reddish (incandescent), the stone appears red. (Source: www.multicolour.com)
Largest Alexandrite: rough: "The Saurer Alexandrite" from Brazil (122,400 ct). Faceted: 66 ct, at the Smithsonian Institution in Washington D.C. (source: www.alexandrite.net)
Deposits: Brazil, India, Russia, Tanzania, Australia, Madagascar, Myanmar, Sri Lanka, USA, Zimbabwe
Name: in honor of the Russian Tsar Alexander II
History:
• Discovery: 1834 at the emerald mines on the Takowaja river in the Ural Mountains (Russia) by the Finnish mineralogist of Tsar Alexander II., Dr. Nils Nordenskjold (after Witali Repej / Ukraine).
• Naming in honor of Tsar Alexander II. in 1842. Alexandrite was named on the occasion of the full legal age of the tsar.
• Discovery of valuable alexandrite in 1987 at Hematita / Minas Gerais / Brazil.
• Resumption of the Takowaja river mine(s) in 1995.
• Discovery of alexandrit deposits in the Araku Valley in Andhra Pradesh / India in 1996.
• Destruction of the coastal mines in India by the tsunami in 2004.