Citrine Quartz,the yellow,orange,reddish-orange is almost
completely created by heating Amethyst.If you see a piece in
nature,it was orignally Amethyst and was heated in nature to
450C,and changed to Citrine.The progression and temperatures to
effect changes in Amethyst is 390C to lighten very dark
material,it fades all the way to (clear)white,then at 450C
returns color as Citrine.Some are more stubborn and need
tempertures up to 550C.Over 500C for extended periods and Quartz
can go to White again.Some can be restored by irradiation to
50-100 megarads,Gamma.Many an impatient treater has opened the
furnace door prematurely,seeing the middle step of clear material
assumes he has over heated.The progression is
Amethsyt,clear,Citrine,clear. This process is done
professionaly,primarily on the Amethyst that is pale,or is
showing zones or brown body color.These brownish ones give the
best darkest Orange color.The primary producer of the world’s
citrine is Brazil,most notable Rio Grande do
Sul,Maramba(Para,State),and Brezeina,Bahia.The better
colors,going into reddish are produced in Rio Grande do
Sul(mulitonnage annually),and Maramba(a production in
decline).The material from Bahia has an overall lighter and more
brownish cast.The Amethyst in Uruguay when heated turns to either
a lemony yellow,or a very dark reddish brown.Here I want to
mention the term “Madeira”,this is often misused to describe the
better colors resembling Imperial Topaz.In truth,the word
“Madeira” is the dark reddish or brown inferior material.The word
Madeira in Portuguese is a color description translates reddish
brown. To further confuse the issue,some Smoky Quartz,irradiated
in Nature,will heat to a lemon or even greenish Citrine on lower
temperatures of 3-400F.In the last few years,there has been quite
a bit of development to irradiate some clear quartz to induce
color. On dosage of 50-100 megarads,gamma,the clear quartz goes
to opaque Smoky color,then is heated in just a household toaster
oven at 3-400F to create mostly yellow,but all colors of Citrine
can be achieved,depending the origin of the material,including
Green.Not all clear Quartz will irradiate to color.Some go only
Smoky Quartz,and for this you use dosage very low,.5-1.5
megarads,gamma.In Brazil,and worldwide there is a cousin of the
Rose Quartz,often termed “milk Quartz”.A clear material with
light to heavy silking. This material goes 100% Lemon Citrine
when irradiated,and subsequently heated.All except the “Conga
Rosa” mine which may be the worlds only source of Rose Quartz
terminated crystals,which goes strawberry Red when processed as
above. A real interesting true story,in Brezeina,Bahia,Brazil the
citrine is more often made by burying the brownish Amethyst to
cook in the sandy ground outside with just the near equator
sunlight.Due to the expense and time to procure an electric or
gas oven,and the operational costs,lack of electricity in these
remote mining areas,this is the preferable method. Another
strange one,is the Bolivian Amethyst/Ametrine(citrine and
Amethyst in one stone).The “Trine” or Citrine part is naturally
occuring.If you heat the “Trine” to clear,then irradiate to 60
megarads,it returns as solid Amethyst. For those interested,I have
written a bit more with photos on this subject at my website at
this URL
http://www.liccini.com/Treating/Quartz/Quartz.htm
Mark Liccini
http://www.LICCINI.com
Exhibiting Tucson GL&W show,Holiday Inn Broadway,Rm.122 Mezzenine