aMETRINE

Photo of an emerald cut, bicolor quartz known as ametrine, set in a custom 14K gold pendant. (Half amethyst, half citrine)
Emerald cut ametrine pendant
Variety:  Ametrine
Species:  Quartz
​​Mohs Hardness:  7 out of 10
Color:  Bicolor combination of purple and orange hues
RI:  1.544 to 1.553 (very constant)
Birefringence:  0.009
SR/DR/AGG:  DR
Clarity Type:  Type II
Optic Character:  Uniaxial positive.  Might show a bull's eye or Airy's spiral optic figure and Brazil law twinning under crossed polarizing filters.
Pleochroism:  Very weak.  Different tones of yellow and orange, different tones of purple and reddish purple
Spectrum:  Not diagnostic
Fluorescence:  Generally inert.
SG:  2.66 (+0.03 / -0.02)
Routine Treatments:  None
Additional Enhancements:  Heating, iraddiation

ametrine Facts

Ametrine & diamond ring, in 14K gold, by Clyde Duneiere
Ametrine and diamond ring

Ametrine is a bicolor variety of quartz that has zones of purple (amethyst) and golden yellow (citrine) that border one another within the same gem crystal.

Amethyst + Citrine = Ametrine
​
The Anahi mine in Bolivia is the world's only commercial source of ametrine.  It has been producing ametrine since the 1600s and is still active today.