The following information is from the website:- http://en.wikipedia.org/wiki/Ametrine
Ametrine, also known as trystine or by its trade name as bolivianite, is a naturally occurring variety of quartz. It is a mixture of amethyst and citrine with zones of purple and yellow or orange. Almost all commercially available ametrine is mined in Bolivia, although there are deposits being exploited in Brazil and India.
The colour of the zones visible within ametrine are due to differing oxidation states of iron within the crystal. The different oxidation states occur due to there being a temperature gradient across the crystal during its formation.
Artificial ametrine can be created by differential heat treatment of amethyst.
Most ametrine in the low price segment can surely be assumed to stem from synthetic material. Since 1994 a Russian laboratory has perfected the industrial production of bicolored quartz crystals that are later irradiated to bring out the typical ametrine colors. Green-yellow or golden-blue ametrine does not exist naturally.
The hardness (Mohs scale) : 7.0 - lower
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The word ametrine is from the three alphabets 'ame' of amethyst (amethyst is the purple color quartz) plus the five alphabets 'trine' from citrine (citrine is the yellow color quartz) = ame+trine = ametrine.
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