Talk:Opal

Merging Ethiopian Wollo (Welo; Wello) Opal into Opal Article

I took the liberty of copying the Welo Opal section into the Opal article. It needs a lot of work, including citations. I believe that the statistics on the percentage of precious opal coming from various countries needs updating, as Ethiopian opal seems to be very common and Australian opal production seems to be declining. Please help edit this newly added section. Dpulitzer (talk) 19:49, 18 September 2014 (UTC)

There is obviously no reason NOT to do this. The Opal article covers many different varieties of opal: Australian, U.S.A., Honduran, Mexican, and others. I am not sure how the merger would take place, as I am relatively new to Wikipedia. Perhaps somebody with more experience can weigh in. (I took the liberty of moving this subject to the top of the list, as the suggestion for the merger appears at the top of the Opal article and it is new). Dpulitzer (talk) 21:47, 16 February 2014 (UTC)

On the other hand, Ethiopian Opal certainly is worthy of having its own article. Ethiopian opal is a form of opal. How much "lumping and splitting" is done on Wikipedia in general is not known to me. (Not well enough to make a final decision, at least). Dpulitzer (talk) 21:59, 16 February 2014 (UTC)

A gel?

This article read 'Opal is a mineraloid gel'... I'm pretty sure that was a typo. Sergeirichard (talk) 17:06, 27 December 2010 (UTC)

Value of opals

Opal is the [Queen of Gems]. No gemstone can match its spectacular 'play of color' or uniqueness. Australia produces 95% of the world's opal. Australian opal is sedimentry, whereas other opal from countries such as Indonesia, America, Peru, Mexico, Hungary and Poland is mostly volcanic.

Quality opal commands a lower price per carrot than diamond and is magnificent.

• If you are familiar with the Rappaport Diamond Price Report, you will find that your statement is false regarding price per 'carrot', I think you mean carat, don't you? We can agree that high-quality gem grade opal is magnificent, but diamonds are graded on an established scale of quality while the valuation of opal is much more haphazard.T.E. Goodwin 07:48, 1 December 2006 (UTC)

I would find it useful if somebody could contribute a description of what criteria are used to determine the value of an opal. PK 08-May-2009 —Preceding unsigned comment added by 93.97.37.147 (talk) 22:17, 8 May 2009 (UTC)

Opal has carrots? 🥕 – AndyFielding (talk) 14:06, 21 February 2022 (UTC)

Formation

There should be something on how opal forms

• I concur. The geogenesis of opal is very interesting but complex to describe. As a Graduate Gemologist, I deal with opals on a daily basis and have been studying them for over 27 years. I will try to add some information on the fly here when I can find some time to go through my past lecture notesT.E. Goodwin 07:55, 1 December 2006 (UTC)

I hope that something is mentioned of the work of Len Cram, an Australian opal expert who has apparently been able to grow "natural" opals (simulating the way they were created in nature) in his home with a mixture of electrolyte, silica, water, alumina and feldspar. This technique produces opals indistinguishable from natural opals, unlike the synthetic ones currently mentioned in this article, and it overturns previous theories of opal formation involving sedimentary depositing of silica gel over millions of years. I am just a layman on this topic but that is what I have read. Lomacar 22:50, 1 December 2006 (UTC)

A Nov 27, 2007 Physics World article (http://physicsworld.com/cws/article/news/31941) by Hamish Johnston provides some information about the formation, composition and new methods of finding opal based on new research that shows that uranium is present in opal. More information is available in The Australian Gemmologist (2007) 23, 160-176, available online at http://www.australiangemmologist.com.au/images/1207opalarticle.pdf

Geologist Brian Senior and physicist Lewis Chadderton have determined that the optical properties of opal stem from the inclusion of tiny quantities of uranium during formation of the stone. Precious opal's play of color is caused by diffraction of light in a regular superlattice of 200 nm silica spheres. The superlattice forms as a result of the presence of the uranium and its decay products which act as seeds for the silica spheres during sedimentation.

The researchers have developed a method of opal hunting based on detection of gamma ray emissions from the decay of uranium contained in the opal. By drilling 3 holes and taking gamma ray measurements at small intervals the team has been able to triangulate the approximate location of opal deposits. The article from The Australian Gemmologist provides great detail of this method and results of field tests.(anon 9:25 CST Dec 14 2007) —Preceding unsigned comment added by 65.174.156.30 (talk) 15:39, 14 December 2007 (UTC)

Article problem

See this slashdot comment:

How do tech-savvy people use it? Not at all. (Score:1) by MsWillow (17812) * Alter Relationship on Friday October 07, @01:12PM (#13736584) (Last Journal: Monday October 03, @03:42AM)

The few times I've checked it against other, reliable sources, it's failed miserably. I'm an avid lapidary. One gemstone near and dear to my heart is precious opal. I checked Wikipedia here [wikipedia.org] for what causes "play of color." They're claiming it's an interference pattern caused by parallel plates formed inside the stone. That's wrong.

Opal is amorphous. It fractures with a conchoidal shape. There are no microscopic parallel plates in opal, tho there are in labradorite. Opal's color play is caused by a regular pattern of silica microspheres, all the same size, forming a diffraction grating.

Opal's colors are pure like a rainbow. You'll never see metallic bronze, or metallic gold, coming from an opal, because of this, but you will see them coming from labradorite.

Their explanation was shown false some 25 years ago, with scanning electron microscope photos of precious opal. Why are they propagating a factual falsehood? And, more importantly, if they do this on a subject that I know well, what happens on subjects where I know little? How can I trust them???

Additional article problem

The article claims that 'opalescence' is often used erroneously to refer to what is more accurately termed 'play of color', but Merriam-Webster defines the adj. opalescent as 'reflecting an irridescent light', and irridescence is defined as 'a lustrous rainbowlike play of color caused by differential refraction of light waves.' Maybe there is a conflict between technical and common definitions, but if MW supports the use of 'opalescence' to refer to 'play of color' in common speech, I believe it. Can someone address this? It sounded like whoever wrote that in the article knew what they were talking about, so I'm hesitant to change it without consultation. cmac 03:27, 30 December 2005 (UTC)

Rather than "play of color," wouldn't the correct term be pleochroism? user:mapetite526

• "Play of color" is the commonly recognized gemological term. Because opal is singly-refractive isotropic, rather than doubly-refractive anisotropic, it cannot display pleochroism.T.E. Goodwin 07:32, 1 December 2006 (UTC)

Superstition

I've heard that opal is bad luck to own unless it's your birthstone. Can anyone confirm that this is a more widely-known belief? --Clay Collier 05:28, 23 October 2006 (UTC)

I've heard this too, I don't believe it though. I own an opal ring but am August born. But yes, someone mentioned this to my Mother once I think. --GracieLizzie 12:27, 17 November 2006 (UTC)

• According to "Gems" 4th Edition by R. Webster, pg. 230 ,"From Roman times until the early seventeenth century it was held in high esteem, but during the eighteenth and nineteenth centuries it fell into disfavour in the belief that the stone was a bearer of ill-fortune, a belief which was probably based on a Teutonic superstition. Others say that this disfavour came from the influence of Sir Walter Scott's novel 'Anne of Geierstein' in which opal played such a malignant part. It seems more probable, however, that Scott concieved the idea of an opal of evil influence from an already exisitng belief."

T.E. Goodwin 07:11, 1 December 2006 (UTC)

Merge

The result of Wikipedia:Articles for deletion/Boulder opal was that Boulder opal should be merged into this article and redirected. If someone more familiar with the topic could merge the relevant details and then redirect Boulder opal to Opal, that would be great. Thanks! ···日本穣^{? · Talk to Nihonjoe} 23:33, 3 January 2007 (UTC)

Hasty decision! An article only weeks old gets slated for deletion... Boulder opal is very distinct from solid opal and should eventually have it's own article. SauliH 07:43, 22 January 2007 (UTC)

Boulder opal is indeed a different "animal" and certainly deserves it's own article, SauliHT.E. Goodwin 23:20, 30 September 2007 (UTC)

Merged a little, most redundant or not really useable. Made redir. Seems boulder opal is simply opal as either fracture fillings or concretions in a dark ironstone - can't really see that it needs a separate article, don't need to promote it for the Aussies. Gem variety articles are mostly spam attractors. Vsmith 12:02, 22 January 2007 (UTC)

What are the limits of coverage of this article?

I see that this page is "supported" if that is the right term by the Gemology & Jewelry project. Therefore, I am not sure whether that would limit adding short sections on the following:

(i) what is known about the "structure" of opal/opaline silica; e.g. opal-C opal-CT, opal-AG etc.. which have slightly different structures on a more local scale. This might not interest gemologists so much as mineralogists/crystallographers, but it would seem to be quite useful to have a resume on here.

(ii) opal is classed as a natural photonic crystal. The page on this topic links to this page and has a picture which was probably originally uploaded for this page. Do a search on Google and see how many links come up under opal & photonic crystal. There is rightly a completely separate page on this topic, but I think it would be good to put a link to photonic crystals somewhere on this page, at the very least under "See Also", since a lot of other people looking up opal might be coming from this field. Opal is almost iconic in this field.

(iii) Organic occurrences of opal/opaline silica: in leaves, some animals etc.

I think these topics should be covered somewhere, but I don't want the anger of the world's gemologists on my head. I'd like to hear some comments on whether people would like short sections at the end of this article or to think about a separate page. Personally, my preference would be to add such sections to this article, since that would fit what I think should be done in an encyclopedia. Judge Nutmeg 15:22, 2 March 2007 (UTC)

Since there were no howls of outrage to my suggestion, I added a contribution on local structure of opal Judge Nutmeg 15:42, 14 March 2007 (UTC)

Technical Problem: The Andamooka Opal reference, which refers to Queen Elizabeth II, links to the RMS Queen Elizabeth II (the ship) when it should, I assume, go to the monarch. Unless someone presented the Andamooka to the RMS QEII.

30 April 2008 Edits

I couldn't quite figure out how to undo some vandalism so I just saved an earlier version of the article. It looks good now. Sorry that I didn't post edit summaries. Makeemlighter (talk) 04:02, 30 April 2008 (UTC)

Birthstone

I have proof that Opals are the October Birthstone but it doesn't say that on that anywhere, can someone help? —Preceding unsigned comment added by 67.171.70.92 (talk) 22:34, 17 September 2008 (UTC)

Relevant to geologists

This page and most of the gemstones are relevant to geologists too. —Preceding unsigned comment added by 138.88.34.53 (talk) 23:00, 10 December 2008 (UTC)

Igneous, Metamorphic, or Sedimentary?

I dont think it is clear weather this would be classified as Igneous, Metamorphic, or Sedimentary.

Superscout22 (talk) 02:08, 15 January 2009 (UTC)

Need pics of the opalized fossils

Bones, teeth, fishes and a snake head, all made of opal? Pics or didn't happen. --TiagoTiago (talk) 10:07, 9 December 2009 (UTC)

Over a decade ago, I bought a copy of "Australian Geographic" with an article about an opalized platipus skull with pictures. If I find the magazine as I clean this fall, I will post the date.Forrestlowe (talk) 22:24, 27 August 2010 (UTC)

File:Opal from Yowah, Queensland, Australia 2.jpg to appear as POTD soon

Hello! This is a note to let the editors of this article know that File:Opal from Yowah, Queensland, Australia 2.jpg will be appearing as picture of the day on January 10, 2011. You can view and edit the POTD blurb at Template:POTD/2011-01-10. If this article needs any attention or maintenance, it would be preferable if that could be done before its appearance on the Main Page so Wikipedia doesn't look bad. :) Thanks! howcheng {chat} 19:12, 5 January 2011 (UTC)

Picture of the day

A polished sample of opal, a mineraloid gemstone, that occurs in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt. Opal comes in a wide variety of colors, with red against black being the most rare, whereas white and green are the most common.Photo: Noodle snacks

fringe stuff
The following discussion has been closed. Please do not modify it.
opal and its effects As all knows that opal is a gemstone for Venus(shukra).Their are various categories which shows its effect for the person who wears it. opal reduces negative thoughts,helps to healing from cronic disease and help to improve the affect of impotency in mens due to aging reason or due to bad practices in male at smaller age. opal initiates charm in doing things and also cure mental problems. fire opal : luck stone,effective in heart diseases,blood pressure. white opal(milky):improves the bone marrow and help to recovering from back acche. —Preceding unsigned comment added by 122.163.65.102 (talk) 15:04, 6 January 2011 (UTC)

Percentages

"Opal is the national gemstone of Australia, which produces 97% of the world's supply,[4] and also of the state of South Australia, which produces around 80% of the world's supply.[5]"

That can not be true. Those numbers add up to a staggering 177%. — Preceding unsigned comment added by 213.185.28.194 (talk) 17:50, 12 August 2012 (UTC)

Since South Australia remains a part of Australia - then it indeed can be true. Altho' the sentences could be worded better. Vsmith (talk) 20:58, 12 August 2012 (UTC)

Reworded, Vsmith (talk) 21:02, 12 August 2012 (UTC)

How is opal formed?

It would be really nice if the article spoke in detail about how opals form ... especially since they seem to be able to form as a replacement in a sort of fossilization process. This should either be in the introduction or an early section. — Preceding unsigned comment added by 98.155.76.35 (talk) 02:00, 11 November 2012 (UTC)

Comment

"The internal structure of precious opal makes it diffract light." Speling12345 (talk) 8:22, 13 December 2013 (UTC)

Ethiopian opal is one of the best opals in the world. It is different from the Australian opal because first, the color. There are many varieties of color. Second, the quality. It will not craze or crack once it is cured. I bought this opal for the last five years and have had no problems in crazing and none of them were fake. As mentioned in Wikipedia, there is a smoked black opal from EThiopia. This is not true because there is no shortage of opal in Ethiopia and Ethiopian people are not in the business of faking other people in regards to their opals. Wikipedia is typically known for having educational material that is non-biased. I would recomend that this website be altered to include the truth about opals from all areas of the world. — Preceding unsigned comment added by 69.145.91.95 (talk) 19:05, 26 July 2014 (UTC)

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Assessment comment

The comment(s) below were originally left at Talk:Opal/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Comment(s)

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Talk page contains some serious questions about facts in the article. These may have been corrected (or not), but inline citations would assist greatly in verifaction. Expansion of sections needed also. Subspecies currently grouped under this article. Breakout as article length dictates. Opal Grading not covered sufficiently. Opal and mythology behind/origin bad luck SauliH 17:22, 30 January 2007 (UTC) Subspecies that should find mention: Black opal Boulder opal Cacholong Opal matrix Girasol opal Lechosos opal Prase opal Menilite Moss opal Hydrophane Ceylon opal Fire opal Hyalite Harlequin opal Hungarian opal Koroit opal Mexican water opal Milk opal Potch opal Opal doublet Opaline Resin opals Treated opal black Triplex opals White opal Wood opal Yowah Nut SauliH 17:27, 30 January 2007 (UTC)

Last edited at 17:27, 30 January 2007 (UTC). Substituted at 01:53, 30 April 2016 (UTC)

"harlequin opal"? No mention?

A google search, and for sale on eBay, render quite a few mentions of "harlequin opals", but no such mention on WP. 66.96.79.217 (talk) 00:21, 1 August 2016 (UTC)

Suggestion to add 'The Royal One' Opal

Suggestion to add 'The Royal One' Opal, at 306 carat it's almost double the size of the Aurora Australis. It was sold in Vegas for $3M USD in 2013, so there's also a need to edit the claim of "most valuable" opal which as currently stand is for the largest but was valued in 2005 at $2.5M AUD. This may very well still be the most valuable but an updated valuation would be needed to justify the claim. EAS (talk) 04:20, 20 November 2016 (UTC)

References to support this? (see WP:RS). Vsmith (talk) 00:55, 21 November 2016 (UTC)

Lead image

Seems the lead image was recently changed to a gem picture with the comment "...Arguably, better to show opal at its best as a gemstone." I've undone that. So, if it is better - then please explain why here. Thanks, Vsmith (talk) 20:25, 10 August 2017 (UTC) Seems the article is about the mineraloid opal. The fact that the mineraloid is used as a gemstone is important ... and well discussed. The images are virtually all about the fancy stuff with little about the more common rock. And commons has lots of fancy pics and almost nothing showing plain opal - and I understand that - nobody wants to add a pic of common stuff. Vsmith (talk) 20:33, 10 August 2017 (UTC)

I am sorry that I did not see this earlier. The "talk page" is obviously the proper forum for the discussion of controversial topics and different viewpoints. I apologize for changing the lead image back to the gemstone image without discussion, and regret having provided such a cursory explanation of the reasoning behind the change(as alluded to above). The mineralogical aspects of opal are preeminent and it is certainly appropriate that the lead image reflect this undeniable fact. I do, however, believe that there may be other considerations in the choice of a lead image: In days past, all textbooks in the natural sciences had plain covers, with only the title and author(s) on the front (cover) and spine. Scientific journals also used this "front cover / spine" format. Today, the covers of most scholarly publications (both textbooks and journals) contain brilliant color images (in addition to the title and author[s] name[s]). These "cover changes" evolved slowly, in apparent lockstep with advances in technological capabilities. Yet, it is not possible to discount the influences of other factors in this "cover revolution." The marketing industry long ago learned that interest in a product or event could be greatly enhanced by utilizing interesting or even provocative color images. As a member of the "old school," I do not need my textbooks and journals to have bright color images, but the publishers apparently do not seem to care. Perhaps this a reflection of changes in attitudes in our rapidly evolving, technologically advanced world. Wikipedia, a living, evolving entity, embodies and embraces change, both informational and cosmetic in the presentation of data. I personally believe that the desire to acquire knowledge should come from within, but if pretty images will attract more people to learn and perhaps become involved with our living tome of knowledge, I must acquiesce. It is regrettable, but I sincerely believe that the Opal page will be viewed (and hopefully studied) by more individuals if the lead image is as visually interesting and attractive as possible, assuming that it is appropriate to the general topic, "Opal." I believe that the use of such an image would not detract from the important mineralogical and other scientific information of the page.Dpulitzer (talk) 01:46, 1 October 2017 (UTC)

And ... why would an image of a finished gem be more attractive (as in attention grabbing) than the current image? The article is not titled Opal gemstones and is not primarily about finished gems. The article is about the mineraloid itself the chemistry, mineralogy, geologic setting, geographic distribution and not just the gem. I do understand that gem fanciers an dealers are more interested in the finished product and making a sale ... however, we aren't here to help them make a buck - just to provide balanced and non-promotional information to the reader. Vsmith (talk) 02:18, 1 October 2017 (UTC)

Your comments are appreciated and respected. Your innumerable contributions to Wikipedia are laudable. A finished gem is probably more attractive than the rough opal because it is more colorful. I do, however, believe that your rationale for the lead image is reasonable and on technical grounds, irrefutable. Perhaps a compromise would be to use the third image on the page as the lead image? It is rough opal and is, in my opinion, more colorful and attractive than the current lead image. You have earned the right to call the shots, so I will leave it to you.Dpulitzer (talk) 19:34, 4 October 2017 (UTC)

Sedimentary vs Volcanic.

As an opal dealer I deal with both Australian and Ethiopian Opals. It is my understanding that Australian Opal is sedimentary and Ethiopian Opal is volcanic. A discussion of the formation of different types of opals should be included. — Preceding unsigned comment added by Rinda Edgmarbou (talk • contribs) 02:00, 25 October 2019 (UTC)

Opal is formed in situ by the deposition of dissolved silica derived from the chemical weathering of other pre-existing rocks, which may be of many types, including sedimentary or volcanic. This deposition of silica is very much a secondary process and in different physical/chemical environments can form minerals such as chalcedony, chert, flint, siliceous sinter, or opal.Bahudhara (talk) 04:27, 3 February 2021 (UTC)

Can Opal be Radiactive?

Just heard from online source that Opal is radioactive via gamma rays. Not sure this is correct may some are but most times I doubt that all Opal is radioactive. — Preceding unsigned comment added by 2402:6940:206:C00:2083:103:9E13:18A3 (talk) 01:35, 2 February 2021 (UTC)

Nope. Bahudhara (talk) 04:27, 3 February 2021 (UTC)

Lede doesn't mention economic or cultural significance of opals

Presumably opals, or precious opals are important gemstones, but the lede doesn't cover this. It should probably be added in some form.Park3r (talk) 19:46, 19 February 2021 (UTC)

The formula

I don't understand the formula -Muonium777 (talk) 14:55, 6 March 2021 (UTC)

Proposed merge of Wood opal into Opal

Wood opal is categorized under Opal.. Wood opal is also not recognized on the List of minerals recognized by the International Mineralogical Association. Therefore, wood opal is better seen as a type of opal.

Wood opal is would also be a type of petrified wood. — Preceding unsigned comment added by David Condrey (talk • contribs) 11:46, 10 July 2023 (UTC)

Notes

{{reflist|refs= David Condrey ^{log talk} 10:46, 10 July 2023 (UTC)