Black Opal Brightness and Body Tone Guide
Vodič za svjetlinu crnog opala i tjelesne tonove
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black opal brightness and body tone guideThe Opal Body Tone Guide was designed and created by the Opal Association of Australia and acts as a guide for Black Opal and Boulder Opals. The Opal industry has recently also been using this guide for many Opal types including Ethiopian Opals.

Body Tone N1 - N4 - Is for black tone body types.

Body Tone N5 - N7 - Is for light coloured Opals mined also at Lightning Ridge but these lower body tone grades can and have been used on Coober Pedy Opals and Ethiopian Opals.

Opal Brightness Guide

The Opal Brightness Guide assists in assigning a value to how bright an Opal is to the naked eye.

Opal brightness can be described as

  • Vivid

  • Very Bright

  • Bright

  • Moderate

  • Subdued

How is Opal Color Produced? Opal formation

The local name given potch, such as desert sandstone, is dependent upon the area in which they occur, but they all belong to the same families of felspathic sandstone, claystone, siltstone and mudstone, which are said to have been deposited over large areas buy streams and lakes.

We call any material that opal colour has formed on as Potch. Except for volcanic opal, which usually occurs in Tertiary rocks, all the types of opal we have come to know so well are found in these strata. Although the opal is found in the Cretaceous sediments, it is a matter of conjecture as to it’s deposition over millions of years during the Tertiary period. The general teaching is that certain minerals were broken down in the country rock to produce silica at 120 parts per million, and trace elements which were deposited in cavities left by bones, shells and other dissoluble material. These, as well as faults and fractures in the ground, provided pathways for the underground waters to carry the silica down at the end of the weathering period.

Although this is the entrenched theory, with “slight variations” depending on your source of information, it is fraught with problems which have been deleted from the model to give it credence. There is little doubt that all opal was not deposited in exactly the same manner. So far I have discovered four different ways in which it has been deposited; there may be more. They all have a common denominator in the equation, ionic-exchange. The fact is that opalization is extremely regional and that large beds of impervious barriers are only secondary to opal formation.

If the only requisite for opalization under the above model were suitable impervious traps, then there would be massive beds of opal over vast areas. However, as every opal miner knows, this is not the case and all opal is unpredictable and patchy in the extreme.

Australian Opal is rarely faceted, nearly always domed. A domed stone is stronger and less prone to chipping. However Opal without a play of color (such as cherry red or amber Opal from Mexico) is often faceted and can look a lot like ruby. Opals are a carver’s delight. The stone is not too hard to work with and will not wear out your diamond tools as much as such stones as Chrysoprase and Agate.

Opal Size

Popular sizes are listed below.

Round: 5 mm and 6 mm

Oval: 6 x 4, 7 x 5, 8 x 6, 9 x 7, 10 x 8, 12 x 10, 14 x 10, 16 x 12, 18 x 13, 20 x 15, 25 x 18, 30 x 22, 40 x 30.

Opal Settings

Jewellery castings for opals can range from very simple designs to very ornate designs with accent diamonds.

There are some interesting myths associated with Opal settings. Some folks believe that Opal Doublets and Triplets are always put into fully backed settings to hide the potch backing. Others believe that full backings are used to protect the stone. Neither myth is true. A jeweler could just as easily “hide” a doublet in an open backed setting, as the join line between the stone and the potch backing would be covered by the side of the setting, making it difficult to see whether the back of the stone was a different stone or simply the less brilliant side of the same stone.

How Opal is Graded and Sold

Rough Opal parcels are sorted into three grades: tops, middle, and low. Each tops parcel has a King stone, which is the best stone in the parcel. Some parcels have several King stones. Color is the primary criteria for grading, but the graders also take into consideration the number of imperfections and faults, and whether a stone is the right shape to be cut into an oval or one of the other popular shapes. You can buy rough opal in several different conditions.

Mine Run

Direct from the mine. The stones have not been cut or ground down. This means that there is more guesswork in the cutting. Purchasing mine run opal can be risky if you are not very experienced.

Off Cuts

The miner has removed whatever black opal rough ,he has a market for and sells you what’s left. With off cuts, you can usually tell what you are going to be able to cut. You must still watch for cracks in the opal because once a crack becomes obvious, a stone can lose half its value.


This can often be the best way of buying black opal rough if you are not very experienced. The miner has cut and ground the stones into basic shapes, after having removed most of the rubbish. What you have left is the stone nearly ready for the dopping and polishing process. You have the satisfaction of cutting your own stones without the high risk of buying mine run rough.

Opal is officially sold in troy oz. There are approximately 30 grams to a troy oz and approximately 30-oz to a kilo.

Hints and Tips

Here’s an eclectic assortment of hints and tips you may find helpful when buying or working with opal.

1. Not all Opal is valuable. Potch, is sometimes called “common opal” does not reflect colors. Potch does have its use, however, as a backing for doublets and triplets. When there is color mixed with potch it’s called “potch and color.”

opal potch

2. Some classes of rough Opal are unsuitable for making gemstones. Some are very porous. Others have a chalky appearance. Still others can lose their color in a short period of time. And yes, it is common for certain types of opals to shatter in a dry atmosphere when the water from the gel evaporates. The best protection for buyers is to purchase opal from a knowledgeable and reputable dealer who accurately details exactly what you are purchasing and is willing to guarantee the stones. Note: If you buy rough opal, there is no guarantee that it will not crack. This is the calculated risk you take and is part of the “excitement” of opal cutting. opal potch

3. When examining opal jewellery, look at the stone from the side to determine whether it’s a triplet. Solid and doublet opal domes are simply the opals formed into a curved dome shape. Triplets have clear crystal domes to protect the flat opal surface.

4. It is very difficult to tell whether a stone is a doublet or a solid if it is in a setting. It helps if the back of the setting is open, but it is still no real indication because the back of a doublet and a solid looks very similar, although a doublet is usually perfectly black on the back whereas a solid black opal usually has some imperfections. So if the back of a stone looks too perfect, you have to be a little suspicious. For this reason it’s best to buy opal from reputable dealers who know what they are doing because, unfortunately, many jewelers also are not experienced in opal.

5. When buying opal over the net, ask the seller to give you a summary of how close the graphic sample is to the real thing. Opal is very difficult to photograph and the appearance on the computer screen may give it a different look. Particularly is this the case in regards to size. Graphics come out in all different sizes, usually a lot larger than actual…so make sure you get your ruler out and actually draw the size on a piece of paper so that you will know in your own mind’s eye the actual size of the stone.

6. The same thing applies to the color of the stone. Make sure you get the supplier to give a commentary on the color so that you will know pretty well what you are getting. The camera sometimes picks up colors that are only minimal, while ignoring the feature colors.

crna opalna svjetlina i ton tijela Vodič za tonove tijela Opal dizajnirao je i izradio Australsko udruženje opala i djeluje kao vodič za crni opal i boulder opale . Industrija opala nedavno koristi i ovaj vodič za mnoge vrste opala, uključujući etiopske .

Tijelo N1 - N4 - služi za tipove crnih tonova.

Body Tone N5 - N7 - Je za opale svijetle boje koji se kopaju također na Lightning Ridgeu, ali ovi niži tonovi tijela mogu i jesu bili korišteni na Coober Pedy opalima i etiopskim opalima.

Vodič za svjetlinu opala

Vodič za Opal Brightness pomaže pri dodjeli vrijednosti koliko je Opal svijetao golim okom.

Najjači od 1 do & Dullest 7 - Može se koristiti na bilo kojem Opalu s 3,5 kao prosječna svjetlina za mnoge opale koji se smatraju komercijalnom ocjenom.

Svjetlina niža od 3 - Smatra se Opal B razreda ili niskom komercijalnom ocjenom.

Kako se proizvodi Opal boja?

Formacija opala

Lokalno ime dade loncu, poput pustinjskog pješčenjaka, ovisi o području u kojem se javljaju, ali svi pripadaju istim porodicama felpatskih pješčenjaka, glinenog kamena, muljevitih kamena i blatnjaka, za koje se kaže da su odloženi na velikim površinama. potoci i jezera.

Nazivamo bilo koji materijal na kojem se opala boja formirala kao Potch. Osim vulkanskog opal-a, koji se obično javlja u tercijarnim stijenama, u tim slojevima nalaze se i sve vrste opal-a koje smo toliko dobro upoznali. Iako se opal nalazi u krednim sedimentima, stvar je pretpostavke njegovog taloženja tijekom milijuna godina tijekom tercijarnog razdoblja. Općenito učenje je da su se određeni minerali razgrađivali u seoskoj stijeni da bi se stvorio silicijum dioksid na 120 dijelova na milijun i elementi u tragovima koji su se taložili u šupljinama koje su ostavile kosti, školjke i drugi netopljivi materijali. Oni su, kao i rasjedi i pukotine u tlu, osigurali putove za podzemne vode da odvode silicijum dioksid na kraju razdoblja vremenskih utjecaja.

Iako je ovo usađena teorija, s „malim odstupanjima“ ovisno o vašem izvoru informacija, ona je obuzeta problemima koji su izbrisani iz modela kako bi joj dali povjerenje. Nema nikakve sumnje da sav opal nije deponiran na potpuno isti način. Do sada sam otkrio četiri različita načina na koji je položen; može ih biti više. Svi imaju zajednički nazivnik u jednadžbi, ionska razmjena. Činjenica je da je opalizacija izrazito regionalna i da su veliki slojevi nepropusnih barijera tek sekundarni u odnosu na tvorbu opala.

Ako su jedini potrebni uvjeti za opalizaciju prema gore navedenom modelu prikladne nepropusne zamke, tada bi na ogromnim površinama postojali masivni slojevi opala. Međutim, kao što zna svaki rudar opala, to nije slučaj i svi su opal nepredvidivi i zakrpljeni u krajnosti.

Australski Opal rijetko je lice, gotovo uvijek je kupolast. Kamen s kupolom je jači i manje sklon sjeckanju. Međutim, Opal bez igre boja (poput crvene trešnje ili jantarnog opala iz Meksika) često je facetiran i može izgledati poput rubina. Opals su užitak za rezbare. S kamenom nije previše teško raditi i neće istrošiti vaše dijamantno oružje koliko kamenje poput krizopraza i agata.

Opal veličine

Popularne veličine navedene su u nastavku.

Okrugli: 5 mm i 6 mm

Ovalni: 6 x 4, 7 x 5, 8 x 6, 9 x 7, 10 x 8, 12 x 10, 14 x 10, 16 x 12, 18 x 13, 20 x 15, 25 x 18, 30 x 22, 40 x 30.

Opal postavke

Lijevanje nakita za opale može se kretati od vrlo jednostavnih dizajna do vrlo ukrašenih dizajna s naglašenim dijamantima.

Uz postavke Opal povezani su neki zanimljivi mitovi. Neki vjeruju da se opalni dupleti i trojke uvijek stavljaju u potpuno podržane postavke kako bi se sakrila podloga. Drugi vjeruju da se za zaštitu kamena koriste pune podloge. Ni mit nije istinit. Nakit može jednako lako "sakriti" dublet u otvorenom položaju, jer bi linija spajanja između kamena i podloge potkopa bila pokrivena bočnim dijelom postavljanja, što otežava otkrivanje je li stražnji dio kamena drugačiji kamen ili jednostavno manje blistava strana istog kamena.

Kako se Opal gradira i prodaje

Grubi paketi Opal razvrstani su u tri razreda: gornji, srednji i niski. Svaka vrhovna parcela ima King kamen, koji je najbolji kamen na parceli. Neke parcele imaju nekoliko Kingovih kamenja. Boja je glavni kriterij za ocjenjivanje, ali grederi uzimaju u obzir i broj nesavršenosti i grešaka i je li kamen pravilnog oblika koji treba izrezati u ovalni ili neki drugi popularni oblik. Grubi opal možete kupiti u nekoliko različitih uvjeta.

Mine Run

Izravno iz rudnika. Kamenje nije bilo posječeno i oboreno. To znači da u rezanju ima više nagađanja. Kupnja opala koji se pokreće može biti rizična ako niste previše iskusni.

Off Cuts

Rudar je uklonio sve crno opalo grubo , ima tržište i prodaje vam ono što je ostalo. Ako nemate posjekotine, obično možete reći što ćete moći smanjiti. Još uvijek morate paziti na pukotine u opalu, jer kad pukotina postane očita, kamen može izgubiti pola vrijednosti.


To je često najbolji način kupnje crnog opal grubog ako niste baš iskusni. Rudar je kamenje izrezao i usitnio u osnovne oblike, nakon što je uklonio većinu smeća. Ostao vam je kamen gotovo spreman za postupak dopiranja i poliranja. Zadovoljstvo ste sjeći vlastitim kamenjem bez velikog rizika da grubo pokrenete mino.

Opal se službeno prodaje u troy oz. Ima otprilike 30 grama do troy-oz i oko 30-oz do kilogram.

Savjeti i savjeti

Evo eklektičnog asortimana savjeta i savjeta koji će vam biti korisni pri kupnji ili radu s opalom.

1. Nisu svi Opal vrijedni. Potch, koji se ponekad naziva i "uobičajeni opal", ne odražava boje. Potch se ipak koristi kao podloga za duple i trojke. Kada postoji boja pomiješana s lončićem, to se naziva "lončić i boja".

lonac od opala

2. Neke vrste grubog opala nisu pogodne za izradu dragog kamenja. Neki su vrlo porozni. Ostali imaju kreden izgled. Ipak, drugi mogu izgubiti boju u kratkom vremenskom razdoblju. I da, uobičajeno je da se određene vrste opala rasprskavaju u suhoj atmosferi kad voda iz gela ispari. Najbolja zaštita kupaca je kupnja opala od dobro poznatog i uglednog prodavača koji točno precizira što kupujete i spreman je jamčiti kamenje. Napomena: Ako kupite grubi opal, nema garancije da se neće puknuti. Ovo je izračunati rizik i dio je "uzbuđenja" rezanja opalom. opal potch

3. Kada pregledavate nakit od opala , pogledajte kamen sa strane kako biste utvrdili je li to trojka. Čvrste i duple opalne kupole jednostavno su opali formirani u zakrivljeni oblik kupole. Trojke imaju jasne kristalne kupole kako bi zaštitile ravnu opalnu površinu.

4. Vrlo je teško odrediti je li kamen dvostruki ili čvrsti ako se nalazi u okruženju. Pomaže ako je stražnja strana postavke otvorena, ali to još uvijek nije stvarna naznaka jer stražnja strana dubleta i punog tijela izgleda vrlo slično, iako je dublet na stražnjoj strani obično savršeno crn, dok čvrsti crni opal obično ima neke nedostatke , Ako vam leđa od kamena izgleda previše savršena, morate biti malo sumnjivi. Iz tog je razloga najbolje kupiti opal od uglednih trgovaca koji znaju što rade jer, nažalost, mnogi zlatari također nemaju iskustva s opalom.

5. Kada kupujete opale preko mreže, zamolite prodavača da vam sažetak koliko je grafički uzorak blizu stvarnosti. Opal je vrlo teško fotografirati, a izgled na ekranu računala može mu dati drugačiji izgled. To je posebno slučaj u pogledu veličine. Grafika izlazi u različitim veličinama, obično puno većom od stvarne… pa se pobrinite da izvučete ravnalo i stvarno nacrtate veličinu na komadu papira, tako da ćete u oči vlastitog uma znati stvarnu veličinu kamena.

6. Isto se odnosi i na boju kamena. Obavezno nabavite dobavljača da komentira boju kako biste prilično dobro znali što dobivate. Fotoaparat ponekad pokupi boje koje su samo minimalne, a pritom ignorira karakteristične boje.

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Over 5 years ago Opal buyers would constantly check and ask questions about Body tone for black opals.
Market trends have now changed, and most buyers ask about Brightness as well as Body tone.
Chinese buyers would only buy N1 body tone black opal and this placed a lot of demand for Body tone ahead of Brightness.
Today Brightness is the most important and has major consideration factor in valuing opals as well as the opal pattern.
Unfortunately we have two systems for Brightness ratings that have not been approved by Cibjo or leading gemmologist organizations.
On Opalauctions we recommend the Australian opal association Opal brightness Guide that places brightest opal at B1. compared to the original B5 rating.

29th Jan 2020

Yes I agree, Brightness should be included on black opal listing.

2nd Jan 2020

Reply Tony translate
Or can we buy the rule Opal base body tone guide SVP
Yes here is link


21st Jan 2017

Ou pouvons nous acheté la règle Opal base body tone guide SVP

21st Jan 2017

Yes.Helped me a lot.Thank you.

3rd Oct 2016

I do get confused with body tone chart with brightness chart.
Its seems everyone states body tone of an opal but I think Brightness is just as important
Lot black opals now seem to be N2 to N3 as an average
I do not see many N1 black opals and they are all expensive now
That’s why I think Brightness is more important now and most are rated B3 to B4
May I make a suggestion that Brightness be added below Body tone on black opal listings

24th Aug 2016

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