Tanzanite 6.1 ct certified

6.10 carat ALGT certified  bluish violet  oval cut natural Tanzanite 

IDENTIFICATION
Species ................................................................................ Natural Zoisite
Variety ............................................................................................ Tanzanite
DESCRIPTION
Shape & Cutting Style ................................................ Oval, Mixed Cut
Measurements .............................................. 12.52 x 9.74 x 6.99 mm
Carat Weight ............................................................................. 6.10 Carat
Color ........................................................................ Intense Purplish Pink
Transparency ......................................................................... Transparent
ADDITIONAL GRADING CHARACTERISTICS
Suggested Origin ......................................................................... Tanzania

MAIN PROPERTIES OF TANZANITE
Chemical Composition ......................... Ca2Al3(SiO4)(Si2O7)(O,OH)
Crystal System ............................................................... Orthorhombic
Mohs Hardness ......................................................................... 6.5 - 7.0
Specific Gravity ...................................................... 3.33 - 3.36 g/cm3
Optical Character ....................................................................... Biaxial+
Refractive Index ............................................................. 1.690 - 1.702
Birefringence ................................................................... 0.006 - 0.012