FMF - Minerals Forum, discussion and message board

[Idahorocks]

Green Quartz _ Prasiolite _ Vermarine _ Green Amethyst or Greened Amethyst

Is the natural green quartz actually a leek green color or does it have other

colors? What other colors are green quartz?

Do all or some have purple in the leek green stone?

I hear that some green quartz is actually heat treated clear quartz, amethyst,

or iolite stone?

Does all of the green quartz have the markings of bands of color like some

amethyst does?

How do I tell the difference between-naturally occurring or manual application

of heat?

In what locations have natural green quartz been found?

[Elise]

[GneissWare]

I am not entirely clear on what you are asking, so I'm not sure if this answers your question.

Most, if not all, green quartz is included with another mineral, thus causing the color.

One of the most common is chlorite, which can form phantoms, where the chorite formed a coating on a crystal face which was later overgrown by more quartz. Sometimes this occurs several times, giving a banded effect.

In the case of prasem, which is strictly a color term not a compositional term, the inclusion is hedenbergite, and the crystals are a leek-green color. The most common localities are Serifos Island in Greece and a Russian locality that escapes me at the moment.

Amethyst and Citrine varieties of quartz are due to Iron in the silicate lattice; the different colors are due to difference in the oxidation state of the Iron. Amethyst has ferric iron, and citrine has ferrous iron. Heating of amethyst will convert tthe ferric to ferrous iron, thus producing citrine. I am not aware of any heat treatment method to produce green quartz.

Hope this is responsive,

[John S. White]

There is just one locality, I believe, in Brazil where some of the amethyst turns green upon heating. Radiation returns the amethyst color. This is well-documented in, among other references, Nassau's "The Physics and Chemistry of Color." According to Frondel "Dana's System of Mineralogy, Vol. III" the locality is Montezuma, Minas Gerais. Amethyst from this locality turns green when heated in air at 510° and then cooled.

[GneissWare]

[Pete Modreski]

From our past discussions here about prase and other terms for green quartz, I'd always been amused by the traditional color descriptor of it as "leek-green", so, when I had the opportunity in our kitchen to observe and record this first-hand some months ago, I took a few pictures. So, here, not a technical contribution but a visual one,
Cheers to all, Pete M.

[John S. White]

That appears not to be the case. According to Nassau: Greened amethyst "can be duplicated by synthesis under reducing conditions, when Fe 2+ is incorporated with two protons for charge compensation. Irradiatiion now ejects two electrons, the first to convert the Fe2+ to Fe3+, the second to form the [FeO4]4- amethyst color center identical to that produced from the yellow Fe3+ containing quartz."
"

[Jon Mommers]

There is also a locality in the Mount Isa District in Queensland that in the 1960's produced pale amethyst that had altered to a translucent mid green colour. The area was not far from Toms mountain.
Once the surface material had been collected, no more of the green was found but the amethyst continued to be recovered at depth ( a couple of metres). I can only guess the mechanism that provided the heat to cause the colour change; during the summer months temperatures normally pass 40C, it is more likely that at some time the area was burnt was bushfires, possibly on numerous occassions over the centuries.

[David Von Bargen]

A good source for info on colored quartz varieties is George Rossman's chapter "Colored varieties of silica minerals" in Silica, a Mineralogical Society of America "Reviews in Mineralogy" vol 29

He lists sites where green quartz has been found including Four Peaks Arizona, Montezuma mine Brazil, Zambia, Poland, Reno Nevada and Thunder Bay.

[Elise]

[Jon Mommers]

Hi Elise,
I am not aware of any references in literature for this occurence, although I will check with some friends at GIA and see if thet are aware of any.
I think I may still have some of this material in storage somewhere, if I locate it I will post some photo's
Cheers
Jon