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The Mineral & Gemstone Ametrine

PHYSICAL PROPERTIES:
Chemistry: SiO 2
Composition: Silicon Dioxide
Class: tectosilicate
Group: Quartz
Crystal system: Trigonal
Fracture: conchoidal
Hardness: 7
Specific Gravity: 2.65
Refractive Index: 1.544-1.553
Pleochroism: weak to distinct
Streak: white
Color: A mix of purple and yellow
Cleavage: none
Transparency: opaque to transparent

DISTINGUISHING CHARACTERISTICS:
The term Ametrine was coined for a variety of quartz in which both amethyst and citrine occur together. The process is not fully understood, but Amatrine is formed, when iron impurities in quartz are affected in different ways. An example of how this could happen is if one side of the crystal was facing a vent or other such heat source. Any change in pressure would affect the temperature forming the citrine and amethyst would begin to form instead.
 
LOCALITIES:
The colors in ametrine have been artificially produced in quartz by irradiation and/or heating. Ametrine rarely occurs in nature. The most well-known natural ametrine source is the Anahi mine in Bolivia.