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Iris Quartz

Last Updated: 21st Nov 2011

IRIS QUARTZ
(aka: rainbow quartz, schiller quartz, iridescent quartz, aurora quartz, anandalite, adularescent quartz)

by Alfredo Petrov and Yuko Tanaka, 21 October 2011
[email protected]

(photos by Yuko Tanaka unless otherwise indicated)

In 2006, a Japanese traveller in India came across crusts of small quartz crystals on sale, which caught his eye because they displayed a peculiar internal spectral phenomenon - flashes of rainbow colours - an interference effect produced by reflection and refraction on very thin parallel Brazil-law twin planes and/or thin depositional layers. (For more detailed discussion of this effect in quartz, see Dr Amir Akhavan's comments on http://www.quartzpage.de/gro_text.html - scroll down about 60% of the way down the long page.) Being of a mystical mindset himself, and recognizing the commercial potential for this material in the esoteric-magical market, the Japanese traveller made a deal with the Indian seller to buy all that he could collect, the earliest specimens having apparently been just picked up on the surface in a jungle area. Later, as the Japanese was still willing to literally buy it all, the Indian dealer hired helpers to dig. Over the next two years, several tons of the material was collected, all destined for one private customer of the Japanese importer, and this customer distributed the quartz in the esoteric market, where it seems hardly to have come to the attention of mineral collectors at all. Both the Indian seller and Japanese buyer kept these intriguing specimens quite secret for two years. But eventually their one private customer could no longer handle the ever increasing quantity being produced and in 2009 the Japanese importer released it to the open market where it created quite a sensation when it first appeared as “rainbow quartz” at various mineral and gem shows in Japan in that year – Nagoya show in july, Japan Jewellery Fair (JJF) in september, Shinjuku (IMAGE show) in october, Ikebukuro show in december... The first cut gems (albeit then still low quality ones) appeared at the IJT show (International Jewellery Tokyo). And of course then the secret was out, and it did not take long before more local Indian dealers got in on the action, eventually increasing production by employing mechanical diggers. One local Indian dealer claims to now have 8 more tons of such quartz, and others have more too. Rumours even talk of 100 tons. Based on what has already appeared on the market, we can assume that only a minuscule proportion is high quality material, with much of the remainder being close to drusy "junk quartz".

Iris quartz from India, rhombohedral face

Yuko Tanaka collection

Iris quartz druse






At first, some people doubted this effect could be natural, and assumed it was due to some unknown treatment, but Japanese gemmologist Professor Kouichi Iida investigated samples and came to the conclusion it was natural, and Iida's certificate of approval, published on the second day of the 2009 JJF show, boosted demand in Japan even more. As will be described in more detail below, other observations and research, some going back over a century, have never found anything to make us doubt that these quartzes could possibly have any other than a natural origin.

In most of the material, the effect is rather weak (or “subtle”, as Amir Akhavan diplomatically expresses it), with the very few more brilliant pieces commanding astronomical prices, up to 1,000 yen (about us$13) per gram, with a decent small cabinet specimen easily reaching us$2,000. Even low quality material sold for 100 to 200 yen per gram. Given the penchant of the Japanese for consuming most of the world’s highest quality products, all the best material has stayed in Japan and only a trickle of mostly unexciting lower-quality material has so far reached the Western world, where it is still little known except to the esoteric folk, to whom this mostly low-end stuff was marketed as “anandalite” and “aurora quartz”, a substance to which an amazing array of mystical properties has been ascribed. One well known mystical marketer hinted that the rainbow colours were caused by its rhodium content! (For this and other hilarious misinformation and magical descriptions, simply google “anandalite” – Amusement guaranteed!)


Iris quartz from India

Two iris quartz crystals.

India

all Yuko Tanaka collection
“Rainbow quartz” was a rather unfortunate name for this material because the term has previously been used for other quartz varieties, including: 1) Colorless quartz crystals displaying interference colours in reflected light on the surface, caused by extremely thin surface films of limonite or other natural minerals – the same effect as caused by thin oil films on a puddle of rainwater; 2) The similar effect induced artificially by coating quartz with a thin film of titanium or niobium by plasma deposition in vacuum (said coatings sometimes alleged in commerce to be “platinum”, “gold” or “silver”, and marketed under names like “aqua aura quartz” as well as “rainbow quartz”); 3) Iridescence caused by natural internal fractures (“crack rainbows”); 4) Fractures created artificially by heating followed by rapid cooling in cold water (“quench cracking”, “Firestone”), with or without the addition of a dye (Leopold Claremont (1917) “Some phases of silica.” The Watchmaker, Jeweler, Silversmith and Optician, October 1917, page 1017); and now, 5) Rainbow colours produced internally by the effect displayed in the specimens under discussion here: very narrow Brazil-law twinning planes or perhaps thin depositional layers. (See also: Waldemar T. Schaller (1918) Gems and precious stones in 1917. Page 160. (USGS publication).) The oldest name for this quartz variety, back in the 19th century, was "schiller quartz" (Schiller meaning iridescence or play of colours in the original german), although the meaning of "schiller" has metamorphosed over time and is now used by gemmologists with a somewhat different nuance. Because of the confusion generated by the "rainbow quartz" and "schiller quartz" names, we will henceforth here use the name "iris quartz", as suggested by quartz expert Dr. Amir Akhavan, analogous to "iris agate".

Going back into mineralogical history, the first example of iris quartz that I could find reference to dates back over 150 years ago, to 1860, when James J. Berkley, a British engineer responsible for developing large parts of the Indian railway network, donated to the British Museum of Natural History the specimen now catalogued as BM 55795, perhaps dug out of a railroad cut, and depicted here in a photo taken by Rock Currier in 1975, unfortunately with the museum lighting being inadequate to display much of its rainbow colours, except minor violet and yellow flashes (eg: in right upper centre). Gerhard vom Rath (rathite), one of the foremost crystallographers of his times, and curator of the mineral museum in Bonn, Germany, had the opportunity to study this specimen during a visit to London in the early 1870s, and published the following comments on it (my translation):


British Museum specimen 55795, 14cm, Aurangabad?; Rock Currier photo
“Mr. Maskelyne, for whose courteous guided tour of the rich treasures of the mineral collection of the British Museum I express my great thanks, was kind enough to show me a quartz specimen from India which – because it displays a perhaps unique phenomenon – is clearly worth mentioning. The specimen in question appeared to represent the rounded end of a stalactitic quartz mass; it is bounded at one end by a flat cut surface and on its terminal stalactite end is comprised of a significant number of approximately 1 cm sized quartz crystals, grouped irregularly next to each other. Viewing the crystal group, one is surprised by a magnificent play of colours, emanating from many parts of the crystals, and which enables these crystals to appear in the various colours of the rainbow – in such manner as I have never before observed in quartzes. On closer observation, it turns out that the beautifully coloured rainbow lies in a plane parallel to the faces of the negative rhombohedron. The schiller is not from the surface, and accordingly appears also in those crystals which exhibit only very minor negative rhombohedron faces. When one views one of these quartz crystals at such an angle that light would be reflected from a –R face, the colourful schiller shines. The crystals are not simple, but rather in part composed of many crystal domains, somewhat like the well known maculose rock crystals from the Alps. Whereas in these latter crystals one can distinguish their polysynthetic structure by meticulous differentiation of dull and shiny parts, as Leydolt taught, after treating the quartz with hydrofluoric acid, which renders it visible to the eye, when the natural habit of a crystal does not permit this: - so too do the quartzes of the indian stalactite exhibit the well known twin intergrowths (by combination of similar individuals in different orientation) in a truly illuminating fashion.” (Gerhard vom Rath (1873) Mineralogische Mittheilungen von Gerhard vom Rath. (Poggendorff’s) Annalen der Physik und Chemie; Ergänzung, vol 6, no. 3, pp 337-386; in: Fortsetzung 12, Abtheilung 2, Anmerkung 4. (1874?) –The paragraph in question is on pp 384-385.)
(Since this publication is hard to find, and available nowadays in only very few libraries, I take the liberty of reproducing vom Rath’s original text in toto in an appendix below (with quaintly antiquated spellings as per the original), for those who may want to read the original language.) This same specimen was studied by another mineralogist the following year too – See: F. Scharff (1875) Neues Jahrbuch für Mineralogie, 636 (which I have not read myself).

The origin of this specimen has been given as “Aurangabad” (by Scharff), a district in Maharashtra state, or somewhere on the Bombay-Poona railroad in Maharashtra, or more vaguely as the Sahyadri (Siahadri) Mountains (= Western Ghats), which cover several states, including the aforementioned Maharashtra districts. More recently, similar specimens have also been found in Jamner in Jalgaon district, and allegedly (but more dubiously) also in Chalisgaon in that same district, and have been sold to tourists visiting the Ajanta caves, a world heritage site famous for its ancient underground temples. The locality for some iris quartz specimens has been ascribed to "Ajanta" itself too, but this may be either because that is just where they were sold - there are lots of crystal sellers in Ajanta - or because the esoteric customers have more appreciation for crystals coming from sites with ancient temples or some other spiritual significance ((as with all the many mystical crystals and tektites that are misrepresented as being from "Tibet")). The same mystical "preference" has motivated at least one dealer to sell the iris quartz crystals as being from the "Himalayas". Note that all of these areas (except the totally spurious "Himalayas") are in Maharashtra state, so we can be fairly certain that the British Museum specimen is really from Maharashtra or immediate environs, as regrettably vague as that is, and it might perhaps even be from the same district as the recent finds of 2006-2010. But... where is the new find coming from? As with most mineral specimens sold in India, locality information is nebulous and unreliable, unless a Western collector has personally been to a quarry and observed the in situ specimens actually being removed from the rock. Much of the time even the Indian sellers themselves do not know the exact localities their wares come from. Most Japanese dealers are just labeling their material vaguely (but honestly) as being from “India”. A few people claim "Ajanta" or "Pune" as their locality, but that is much more likely to represent point of sale than the true locality. One dealer was giving out the more specific “Karvi (or Karwi), Madhya Pradesh”, although Karvi (aka Chitrakoot Dham) is really just a bit over the state border in Uttar Pradesh, and roughly 500 to 700 kilometers ENE of the Maharashtra localities, but this might perhaps be just mystification to keep other willing buyers away, or perhaps there are more "Karvi"s among India's 2 million villages. The most seemingly reliable locality attribution for the abundance of new material is an area just west of Burhanpur, Madhya Pradesh state, near the border with Jalgaon district, Maharashtra state. It is of course entirely possible that iris quartz comes from more than one district in the vast Deccan Traps.


Iris quartz facetted by Colorstone Mithrill, Tokyo

Iris quartz, 3.5cm group from "Madhya Pradesh"; photo by Yuuki Hasegawa
Sir Chandrasekhara Venkata Raman (1888-1970), Indian physicist, Nobel prizewinner, discoverer of Raman scattering in light (which eventually lead to the development of Raman specroscopy), had a special fascination with iridescent minerals and was the first person to undertake detailed technical studies of the phenomenon in iris quartz, in 1950. (C.V. Raman (1950) 
Crystals of quartz with iridescent faces
. Proceedings of the Indian Academy of Sciences, Section A, 31, 275-279.) He found that the rainbow was produced in a zone just 0.25mm wide, with individual layers a mere 0.34 microns thick. “It seems, however, just possible that the polysynthetic twinning may be accompanied by a segregation at the boundaries between the right-handed and left-handed quartz of extremely thin layers of impurity material. Such layers when regularly disposed could give rise to coherent reflections of sufficient intensity to explain the observed iridescence.” (Raman, 1950) The effect becomes visible more strongly by immersion in water or xylene. One face he studied displayed colors that varied from green to blue to bluish violet, depending on the angle of incident light. (And just in case you thought that Sir C.V. Raman, as an Indian scientist, might have had any better information on the locality of these crystals than you and I... No, he just got two iris quartz crystals from a jeweller in Bombay, as usual without any decent locality label.)


Iris quartz (twin?)














Amethyst and quartz geodes from Artigas, Uruguay, yielded a few specimens of iris quartz in 1987. Arizona mineral dealer Jack Lowell called the effect “adularescence” and submitted specimens for study to the GIA, where John Koivula, apparently unaware of the previous studies of this phenomenon, referred to the “adularescent-like phenomenon” which then became known to some in the gem trade as the “Lowell effect”, a rather unwarranted name considering that this type of quartz had already been known for well over a century. Koivula noted some rainbow “curtains” and blue flashes on minor rhombohedral faces in the colourless zones of these Artigas amethyst crystals, not visible in the purple zones. (Gems & Gemology, winter 1987, p 240.) The following year, Lowell’s Colorado Gem and Mineral Co., of Tempe, Arizona, started selling cut gems of iris quartz, as reported in the june 1988 issue of Lapidary Journal. The largest such gem (mentioned in a private letter by well known gemmologist Edward Gübelin) weighed an astounding 5.75 carats!

Then that same year, the winter 1988 issue of Gems & Gemology reported the same phenomenon, with a great photo, in colourless quartz from near Poona, Maharashtra, India (although “Poona” here might be just a generic reference to the Deccan Traps, as is often the case with mineral specimens from India). These specimens had been purchased in India by Meg Easling and Julie Wellings of Gem Quest Jewellers in Ojai, California.


Stereoscopic colour shift!

Compare colour with previous photo.
Since then, iris quartz has been found in several other countries. In October 1996, Klaus Schäfer of Idar Oberstein showed a quartz specimen from Germany which exhibited what he called the “labradorite effect” to renowned quartz experts Si and Ann Frazier of California. The quartz was a very pale citrine, showing iridescence on rhombohedral faces, from Reichweiler, Pfalz, a region of quartz vugs in basalts, not far south of Idar Oberstein.

Gübelin and Koivula (2005) Photoatlas of Inclusions in Gemstones, Vol. 2, 644, display a photo of a colourless iris quartz from Washington state in the USA. Iris quartz specimens are also now known from Turkey, Brazil, Sidi Rahal [[which will be visited by Mindat conference participants in november 2012!!]] in Morocco, the indian state of Orissa (perhaps also mere mystification - See previous comments on India localities), and perhaps Italy too.

Diligent observers may well recognize this phenomenon at other new localities, especially where quartz crystals grow in cavities in trap rocks. Furthermore, collectors should keep an eye out for possible examples of this phenomenon in other minerals besides quartz. (One of the authors - Y.T. - has already observed it in a forsterite crystal from Miyake-jima.)


Sidi Rahal, Morocco; Amir Akhavan photo; Spirifer Collection


Acknowledgements: We are grateful to Kazuhiro Yoshida for background information on recent finds and for clearing up some of the misinformation that tends to surround anything new and desirable; to Si and Ann Frazier for allowing us to consult their astonishingly comprehensive library on quartz; to Amir Akhavan and John Kashuba for their patient and enlightening discussions; to Alan Hart for looking up the “type specimen” at the British Museum; to the Bergakademie Freiberg librarians and Hudson Institute of Mineralogy, who patiently helped track down elusive old references; to Yuuki Hasegawa and Rock Currier for use of the photos they uploaded to Mindat.

Appendix:

Vom Rath’s comments on the "Schillerquarz" in the British Museum, in the original german:

Herr Maskelyne, dessen zuvorkommende Führung in den so reichen Schätzen der Mineralogische Sammlung des British Museum ich mit grossem Danke erkenne, hatte die Güte, mir eine Quarzstufe aus Indien zu zeigen, welche – weil sie eine vielleicht einzigartige Erscheinung darbietet – wohl eine Erwähnung verdient. Die betreffende Stufe schien das gerundete Ende einer stalaktitischen Quarzmasse darzubieten; sie ist einerseits durch eine angeschliffene Fläche begrenzt und besteht an ihrem zapfenförmigen Ende aus einer bedeutenden Zahl etwa 1 Ctm grossen Quarzkrystallen, welche unregelmässig neben einander gruppiert sind. Blickt man auf die Krystallgruppe, so wird man durch ein herrliches Farbenspiel überrascht, welches von vielen Theilen der Krystalle ausgeht und dieselben in den verschiedenen Regenbogenfarben erscheinen lässt – in einer Weise, welche ich niemals bei Quarzen beobachtet. Bei näherer Untersuchung ergibt sich alsbald, dass der schöne Farbenschiller in Ebenen liegt, parallel zu den Flächen des Gegenrhomboëders. Der Schiller geht nicht von der Oberfläche aus, erscheint demnach auch an denjenigen Krystallen, welche die Flächen des Gegenrhomboëders nur sehr untergeordnet zeigen. Blickt man auf einen dieser Quarzkrystalle in einer solchen Richtung dass eine Fläche von –R glänzen würde, so leuchtet der bunte Farbenschein. Die Krystalle sind nun nicht einfach, sondern zum Theil aus vielen Krystallstücken zusammengesetzt, etwa nach Art der bekannten gefleckten Bergkrystalle aus den Alpen. Während man bei diesen letztern durch sorgsames Unterscheiden von Matt und Glänzend die polysynthetische Zusammensetzung wahrnehmen kann, welche Leydolt gelehrt hat, durch Behandlung der Quarze mit Fluorwasserstoffsäure auch dann dem Auge wahrnehmbar zu machen, wenn die natürliche Beschaffenheit der Krystalle dies nicht gestattet: - so zeigen die Quarze des indischen Stalaktiten die bekannte Zwillingsverwachsung (durch Verbindung gleichartiger Individuen in verschiedener Stellung) in einer wahrhaft leuchtenden Weise.” (Gerhard vom Rath (1873) Mineralogische Mittheilungen von Gerhard vom Rath. (Poggendorff’s) Annalen der Physik und Chemie; Ergänzung, vol 6, no. 3, pp 337-386; in: Fortsetzung 12, Abtheilung 2, Anmerkung 4.)

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Comments

Alfredo & Yuko,
Nice article, and thank you for posting it. Some of the specimens and cut stones depicted are quite dramatic, and it is good that they are in color. I am familiar with iris agate and have a number of excellent examples, and I have observed crack rainbows in quartz, particularly on a micro level. I believe I have seen specimens like the ones you describe here as well. It is good to learn more about what causes the phenomenon.
Best regards,
Bob Meyer

Robert Meyer
4th Nov 2011 3:09am
Wow, great article and photos! Rob Woodside and I stopped and marvelled at the booth of one Indian seller of such quartz at Tucson last year. We debated at length about the possible origin of the phenomenon (and the likelihood it was natural). I don't remember if we settled on a conclusion, but I think Rob picked up a couple of pieces "just in case". I bet now he's glad he did!

Thanks gentlemen!

Michael J. Bainbridge
5th Nov 2011 4:33pm
Alfredo & Yuko,
Thanks for the informative article. I have looked for info on these crystals for about 2 years now. I bought several flats of what would be considered the lower-end to medium-end of quality from an Indian dealer who stopped by my store and who insisted it was natural. I almost didn't believe him because I had never seen anything like it before. I wish I had photographed them before I sold them all.


Rick Dalrymple
5th Nov 2011 5:09pm
Great article!!! When Michael and I saw this last Tucson I nearly bought a small one for $200. Unfortunately Michael interpreted my politness towards the dealer as an uncertainty about the effect's cause. They are obviously interference colours from the parting on the rhombohedral faces. The effect appears more strongly on alternate terminal faces which are nearly in equal development. I'm surprised the effect is enhanced by immersion in water or Xylene as this means that the liquid is entering the parting. Last May at Bart's Seattle Mineral Market I bought a 7x7 cm piece with xls points to 3 cm and a little iron staining on the base for $30. I put this piece under water in a position that showed good blue green color in a face before the water was added and within a minute or so some red appeared in the face. Now after several hours there is much more red. This augers ill for cutting this material. I note that when the colour occurs it is often on the edges of the face. I'll remove it from the water now and report back later if it returns to the initial blue green.

Rob Woodside
25th Nov 2011 1:37am
Alfredo told me that the immersion in water or Xylene was only to diminish surface reflections. Raman would have noticed any change in the interference colours occurring on immersion. So his material was cutable unlike mine.

The red patches that occurred on water immersion are smaller in area after being dry for a few days. Applying pressure to that face also diminishes them.

Yes there is iron staining at the base of my piece, but on turning it over it has Celadonite on the bottom! So as Alfredo suspected they are from the Deccan traps and not from the Himalayas as advertised and labelled.

Rob Woodside
1st Dec 2011 7:41pm
Rob, did the colour return to normal after a while after you immersed it in water? I just got a specimen myself but it came in a bag full of pot pourri and it stinks so I want to wash it to get rid of the smell but i like the colours as they are I do not want them to change if I get it wet.

Jason Evans
8th Aug 2012 5:20pm
Alfredo, I very much enjoyed your article which inspired me to get my own specimen, I have a question and it may seem a bit dumb, but regarding the claims from the metaphysical crowd about the colours being caused by Rhodium. You speak of that as if it is a totally ridiculous idea and could not be feasible, whist i do not follow the metaphysical folks and i take the scientific facts more seriously, I am just curious to know why it can not be caused by Rhodium, have there actually been any tests like SEM or XRD to look for the presence of rhodium, or would it show up in such tests? or is there some other reason why it could not be that so its not even worth the efforts to have it tested? Has there been any new info since you wrote this article that confirms the theory of it being caused by diffraction and refraction between brazil law twins, as I understood it that is just the most accepted theory but it has not yet been proven.

Jason Evans
11th Aug 2012 3:49pm
Typically well researched. Thanks Alfredo!

Dave Crosby
25th Mar 2013 8:18pm
A big thank you to Milind Kolhatkar, a very pleasant mineral dealer from Pune, India, who kindly provided some beautiful high quality iris quartz samples for research. He can be contacted via his Mindat home page or by e-mail at [email protected]

Alfredo Petrov
16th Jan 2014 9:43pm

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