General : What Colors Amethyst?

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GeneralWhat Colors Amethyst?

30th Apr 2010 15:40 UTCKristi Hugs OP

I am getting conflicting information as to what is the real "culprit" that makes Amethyst purple. Most agree it is manganese, but recently, I am finding many sites that say it is Ferric Iron (Fe3+) and some say it is both. I am just learning what colors what and I want to be accurate when I make my list, so can anyone tell me decisively, which is it? manganese? or Ferric iron? thank you!!

30th Apr 2010 18:37 UTCR.S.Taylor

That's a good question but iron is a pretty safe bet as iron is also the primary coloring agent of natural citrine and heating amethyst changes it into brownish citrine. The different shades of amethyst and citrine are more than likely the result of other impurities... for instance amethyst with pinkish undertones is probably caused by trace amounts of pink manganese which is also the primary coloring agent of most rose quartz and mangonoan calcite but manganese is also among the iron group of minerals. Testing for the exact coloring agents of quartz is difficult because quartz can contain a large variety of trace minerals and they all contribute to the many subtle variations in color.

30th Apr 2010 19:34 UTCVandall Thomas King Manager

There are a lot of urban legends that circulate. Someone must have guessed that manganese made amethyst purple and that explanation still keeps showing up. Rose quartz used to have its color attributed to manganese or titanium, but about 8 years ago, it was revealed that massive rose quartz had inclusions of a "dumortierite-like" mineral. Before that, it was discovered that the color of rose quartz crystals was due to phosphorus. Similarly, someone did a qualitative chemical test on black dendrites in the nineteenth century and found they contained manganese and concluded that the safest bet was that they contained the most common manganese ore mineral, pyrolusite. In 1979, it was shown that no dendrite specimen tested by modern methods was pyrolusite, even as an impurity. In the 30+ years since then, no dendrite that I know of has been proven to contain pyrolusite. Shaking off old ideas takes quite a bit of time and there are still books coming out with old information.

30th Apr 2010 23:34 UTCKristi Hugs OP

Hey Van, So the ferric iron would be more accurate and up to date (as to what colors amethyst). is there a periodical or some sort of book that I can get that will tell me the most updated information on what colors what? :) thanks!! Kristi

2nd May 2010 15:18 UTCRock Currier Expert

Yes, Iron, water and radiation.

2nd May 2010 16:14 UTCRick Turner

Quartz from some of the Mendip deposits - such as Merehead - is sometimes coloured purple by manganese, but the colour is generally fugitive and fades over time / with exposure to light, eventually ending up as a yucky brown. We suspect that it's due to a (per-)manganate ion of some kind but nobody has tested this hypothesis. This is not 'true' amethyst - as others have already said, Fe is responsible for that - but it does cause confusion by appearing in the literature as either 'amethyst' or 'amethystine quartz'. Any deposit where quartz and Mn are present can do this. Rick

3rd May 2010 01:18 UTCJohn Attard Expert

The Russians have done a great deal of work on colored quartz and as far as I know it is Iron that they use to produce amethyst.

3rd May 2010 23:26 UTCVandall Thomas King Manager

Has permanganate been found in Nature? I thought it was too reactive.

4th May 2010 20:08 UTCRick Turner

No idea.... as I said, nobody has tested the Mendip material. Perhaps I should have qualified the original post as "(per- ??) manganate". Whatever it is, it must be fairly reactive though - sometimes the colour change from purple can happen literally in front of your eyes, over the space of a few seconds. Since it goes into the rock - rather than just being a surface skin effect - it must be a photosensitive response triggered by exposure to light when the rock is broken rather than by exposure to the air/oxygen. However, other pieces are relatively stable in color, so I would expect that there is more than one color-causing mechanism. A reasonable suggestion would be to say that it would likely be linked to the oxidation state of the Mn in some way. A number of the Mendip deposits (e.g. Writhlington, Holwell Quarry) also produce "smoky quartz", where the colour is a brownish black rather than the normal/usual grey-black. I would not be surprised to find that the same mechanism were responsible for this color as for the amethyst - perhaps "smoky" is caused by really minute MnO2 inclusions (e.g. Mn IV) which would suggest that the purple->brown change is due to oxidation, implying that the purple was due to either Mn II or Mn III. Again, nobody has tested this that I am aware of. The only analysis that I have for quartz is for a piece from Merehead that we collected a few years back. It contains a fair amount of Mn, but I'd expect this given that the matrix is comprised of Mn-oxides. Despite the presence of Mn, this quartz is colorless/white, so there cannot be a simple direct correlation between quantity of Mn and color, which tends to support the idea that valence and/or coordination are a more likely cause. Rick

4th May 2010 20:35 UTCRob Woodside 🌟 Manager

O.K. I finally googled Amethyst colours and this Wikipedia note came up. The color amethyst is a moderate, transparent violet. Its name is derived from the stone amethyst, a form of quartz. Though the color of natural amethyst varies from purple to yellow, the amethyst color referred to here is the moderate purple color most commonly associated with amethyst stones. There is disagreement as to the cause of the purple color of the amethyst stone. Some believe that the color is due to the presence of manganese, while others have suggested that the amethyst color could be from ferric thiocyanate or sulfur found in amethyst stones. Previously I had a high opinion of Wikipedia, but not when they put out this outdated BS!!! Some here actually contribute to Wikipedia and I would ask them to fix this nonsense. Some years ago there was a Min Rec note explaining amethyst and smokey quartz. The origin of their colours are well known and due to minute Iron and Aluminum impurites. I'll try to track down some references. (perhaps the second or third google hit???)

4th May 2010 21:00 UTCRob Woodside 🌟 Manager

To my horror the second google ref was to Wikipedia again: Amethyst - Wikipedia, the free encyclopedia "The amethyst is a gem of a violet colour, and great brilliancy, said to be as hard as the ruby or sapphire, from which it only differs in colour. ... I guess you get what you pay for. I had no idea an amethyst was a purple corundumB)- Never the less clicking on the link actually returned information rather than folklore: In the 20th century, the color of amethyst was attributed to the presence of manganese. However, since it is capable of being greatly altered and even discharged by heat, the color was believed by some authorities to be from an organic source. Ferric thiocyanate was suggested, and sulfur was said to have been detected in the mineral. More recent work has shown that amethyst's coloration is due to ferric iron impurities.<1> Further study has shown a complex interplay of iron and aluminium is responsible for the color.<2> Here are the references: ^ Klein, Cornelis and Hurlbut, Cornelius S., 1985 Manual of Mineralogy (after JD Dana) 20th edition, p. 441, John Wiley & Sons, New York ^ Cohen, Alvin J., 1985, Amethyst color in quartz, the result of radiation protection involving iron', American Mineralogist, V. 70, pp 1180-1185 They are only 25 years old and the Min Rec note is more recent. The references appear clickable at Wikipedia, so I'll leave it to you for the details you may wish.

5th May 2010 00:18 UTCAmir C. Akhavan Expert

Rob Woodside Wrote: -------------------------------------------------------> O.K. I finally googled Amethyst colours and this > Wikipedia note came up. > ... > Previously I had a high opinion of Wikipedia, but > not when they put out this outdated BS!!! Some > here actually contribute to Wikipedia and I would > ask them to fix this nonsense. The article "Amethyst (color)" is about the color "amethyst", not the mineral, and it is marked as a stub. Of course you are right that the causes of color given are all known to be wrong since 1925. Luckily they forgot to add boron as another "possible" cause. The article on amethyst (the mineral) isn't all that bad.> The amethyst is a gem of a violet colour, > and great brilliancy, said to be as hard as the ruby or sapphire, > from which it only differs in colour. ... This is part of a citation from a 1827 (!) reference. > I guess you get what you pay for. Not true in the Internet. I will fix this for free, as good as I can. But if you want you can pay me and watch how the quality will be further improved B)- (and btw, I never paid for mindat ;) ). It will just take some time, a few hours, because of lots of references and because the Wikipedia syntax is a bit awkward. I'll drop a line when I'm done in a few days. Actually my own information on this is a bit outdated, too, amethyst-color-wise I live in the year 1995 :( The Wikipedia folks has a lot of trouble to keep the articles "clean". Check out the history on the amethyst article, for example the entry for "16:02, 13 April 2010 ".

5th May 2010 00:45 UTCRob Woodside 🌟 Manager

Thanks Amir, I didn't know you were involved with Wikipedia. Thanks very much for sorting this out. It looks like there are 3 culprits here- me, google and wikipedia. I actually googled amethyst colour and google suggested adding an s and that produced the first quote. It never occurred to me that they were taking about colours and not rocks. The next quote was an out of context selection by google. I never bothered to check the context or see that it dated from 1827. I wonder why on earth google thought it relevant. Anyway you are right about the amethyst article and the final quote gave what was sought. You've restored my faith in wikipedia :S

5th May 2010 01:44 UTCAmir C. Akhavan Expert

I was very confused myself for a minute or so when I read the Amethyst (color) article. I'm not really involved in Wikipedia, I just have an account that I use about once a century. One just needs to be prepared for the flames when one works on an article, but that's not different from Mindat. But if you give good references, there should not be a lot of complaints (I hope ;) ).

5th May 2010 02:49 UTCJeremy Zolan

I forget where I saw it, but I've read that amethyst gets its color from Fe4+. I think this may be a bit of a dubious claim, since tetravalent iron is quite unstable. If anyone can find data to support this, please let me know.

5th May 2010 02:52 UTCJeremy Zolan

Also, I doubt that permanganate occurs in nature. Permanganate is highly reactve- it's an exceptionally good oxidizing agent, which can be used in synthesis in a similar manner to osmium tetroxide. If the purple color is induced by manganese, I'd guess that it's coming from Mn2+ or Mn3+ ions.

5th May 2010 04:48 UTCJohn Attard Expert

I would not expect permanganate to exist in nature nor have I ever heard it does. The color an element imparts to a stone can be and usually is completely different than the color it gives to a compound in water solution. In water many ions are hydrated. Remember even simple copper sulfate is blue when hydrated and almost colorless when anhydrous. Copper gives green in malachite and blue in azurite. While I cannot exclude the presence of Mn in amethyst I do not believe it is permanganate that is doing it. Everybody knows that analysis is often the way to find out what is causing what. When this gets difficult like analysis of trace elements in amethyst there is an alternative and that is Synthesis. Different ions were put into the growing medium of quartz. Iron gave the purple quartz. Other ions produce colors not known in nature. Visit some Russian dealer in a show... like Dimitriy Belakovsky. The amethyst the Russians made is so good that jewelers consider it a threat to their stocks of natural amethyst.

5th May 2010 08:29 UTCDavid Sheumack

I think Rock's comment could be on the mark. Back in the days when Safety and Occupational Health at Uni was unknown, many experiments carried out in 3rd year Nuclear Chemistry involved gamma radiating various solutions with a cobalt-60 source; the source was down a 50ft hole filled with demin water in the department basement. Most of the radiated solutions were in soda glass measuring cylinders or the like. Various grades of soda glass have minor impurities such as iron. And the result.....glass measuring cylinders etc became the colour of rich amethyst.

5th May 2010 17:42 UTCRob Woodside 🌟 Manager

Jeremy, here is the Fe+4 discussion given in the second Wikipedia reference: http://www.minsocam.org/ammin/AM70/AM70_1180.pdf

5th May 2010 19:41 UTCDavid Von Bargen Manager

A good discussion on coloring of quartz is a chapter in the MSA's Reviews of Mineralogy (1995) vol 29 Silica by George Rossman. Unfortunately it isn't online.

10th May 2010 20:00 UTCWilliam G. Lyon

George Rossman's website is online, and is an excellent starting point for learning about the causes of color in minerals. http://minerals.gps.caltech.edu/ Fe(IV) or Fe4+ is the accepted source of color in amethyst. This otherwise unusual oxidation state of iron is produced by ionizing radiation, and preserved inside the solid. Permanganate has not as far as I know been found in minerals. Spectroscopically, it would have distinctive lines from vibronic coupling which would readily distinguish it from other contenders. and/or Mindat.org® is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Mindat® and mindat.org® are registered trademarks of the Hudson Institute of Mineralogy. Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2026, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph and Ida Chau. To cite: Ralph, J., Von Bargen, D., Martynov, P., Zhang, J., Que, X., Prabhu, A., Morrison, S. M., Li, W., Chen, W., & Ma, X. (2025). Mindat.org: The open access mineralogy database to accelerate data-intensive geoscience research. American Mineralogist, 110(6), 833–844. doi:10.2138/am-2024-9486.Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: March 2, 2026 16:36:16 Go to top of page