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Fakes & FraudsDiamonds in Conglomerate from Brazil?

12th Jun 2009 12:14 BSTJolyon Ralph Founder

An example (sorry Paul, not picking on you deliberately)

What's the verdict on the diamonds and gold in conglomerate from brazil - Having looked at them they're highly suspect (based on type of dealers selling them, visible diamonds AND gold in same specimens sometimes.

Have heard rumours that these were assembled and grown from some kind of rusty sludge cement filled with pebbles and the odd diamond/gold nugget and left to harden.

Anyone know any more?


12th Jun 2009 12:51 BSTPaul De Bondt Manager


No problem, I don't feel sniped.

This is the information I have and some remarks I can provide for the moment.

I had my specimen from Werner Radl in the early 90's and must admitt, I did'nt saw some since then.

If they where fake ( what is allways possible off course ) we should see more of them on shows.

I have a few mineral related books where the Diamantina Diamond conglomerates are mentionned, without more details.

The associated Gold seems souspicious.

It is also possible that the specimens does not come from the cited area what adds to the enigma.

It can be the same than with the Katanga minerals. If you don't find them yourselve ( what is prohibited in Congo ) you have to trust the man who sells you the stuff. Most of the times the localities given are 50 miles away from the original place to avoid other diggers to go to the deposit.

To give an idea, according to Wikipedia, Minas Gerais is more than 586.000 km² and France is " only " 550.000 km².

So labeling those Diamond would maybe be more accurate to label them just Minas Gerais, except when the question is solved.

Who knows what treasures still hiding in a territory bigger than France covered essentially with jungle and luxureus plants, and where ?

I keep on searching and will post again if I find something more. It would be interesting to know more about the formation of these specimens.

I hope this helps.

Take care and best regards.


12th Jun 2009 13:21 BSTTony Peterson Expert

Jolyon et al - I had the pleasure of seeing these conglomerates in a field trip/conference many years ago. I also purchased 6 diamonds from a local dealer, mined by hand by individuals from this conglomerate, which I keep meaning to upload pics of. Will try to get that done, and can include field shots of the digging pits in the conglomerate.

The diamonds are of course detrital in the conglomerate, and it is entirely reasonable that they should be found with other heavy minerals, including gold - though I have no information on that. They would of course have different primary sources. The ultimate source of the diamonds is uncertain. It is quite possible that some or all of them came from (now) west African sources, the continents having separated since deposition of the conglomerate.


12th Jun 2009 16:39 BSTRob Woodside Manager

In the mid 80's I found a Brazilian diamond in conglomerate in a dealer's stock. Knowing that South African diamonds would eventually lose their matrix, I asked if it was real, meaning was the xl glued in. To my amazement the dealer said it was another dealer's rock and was actually plasticized!!! He rumaged around for a propane torch and a needle, saying that a hot needle would easily pierce the conglomerate. To both our amazements the "conglomerate" collapsed in a sorry heap at the first touch of the hot needle. I politely declined the specimen.

Tony raises an interesting point about the African origin of Brazilian diamonds. Where are all the Brazillian Kimberlite pipes needed to produce all these alluvial Brazilian diamonds???

12th Jun 2009 16:56 BSTTony Peterson Expert

Rob, there are some, but they are not nearly as numerous or rich as possible African sources.

12th Jun 2009 17:45 BSTRob Woodside Manager

Thanks Tony, I had not heard of any.

12th Jun 2009 18:58 BSTAlfredo Petrov Manager

I bought about 5 of these Brazilian diamonds-in-conglomerate specimens, was initially suspicious, and studied them all carefully under the microscope. The conglomerate looked quite natural: quartz pebbles, various other resistant detrital minerals (kyanite, andalusite...), and a limonitic cement of variable friability; quite typical of indurated alluvial deposits under tropical weathering conditions; certainly nothing synthetic-looking. None of the diamonds popped out after an overnight soaking in acetone. None showed any evidence of fluorescent glue under UV light. I was then convinced they were natural. However, after I cleaned them in warm water, one diamond did come out, and the matrix immediately around it had become soft and plastic - apparently limonite powder mixed with a water-soluble glue that was not affected by acetone or UV light. Now I'm curious how many other people's specimens would decompose in warm water?

But.... I still have a nagging suspicion that something else isn't quite right. Psychology, for one thing. It's very hard to convince Third World miners to sell gold or gems in matrix - they generally optimistically believe there are likely to be more, deeper inside the matrix, so they want to crush everything up, not sell it whole. Why the desire to sell these pieces whole, without breaking them down into smaller pieces? One well-known Brazilian dealer of rare species told me that local suppliers in Brazil did occasionally offer him diamonds in conglomerate but that he did not carry these specimens because he too was suspicious of them, although he had no concrete evidence they were faked. Perhaps it is, like the Congo malachite stalactites, a case of some being real and others faked (glued in).

Incidentally, mine had been labelled as being from the "Rio Formosa do Norte".

15th Jun 2009 22:34 BSTPeter Andresen Expert

Gold and diamonds are found in the same alluvial layers in this deposit, but no chanse to get out a matrix sample, all came out as a muddy mixture...

16th Jun 2009 02:02 BSTRock Currier Expert

I am sure that diamond and gold in sedimentary conglomerate matrix are regularly found in Minas Gerais, Brazil. The problem is that the diggers who are digging for such things rarely own the land they are digging on so are naturally very shy of saying where the things are coming from, and when they do finally get down into the pockets or pot holes where these are concentrated, the last thing they have in mind is to try and salvage specimens. Often in the bottoms of these pot holes where the stuff is concentrated, some of the contents are pretty well cemented, and what is traditionally done is to bust it out of the pockets and break it up to extract the gold and or diamonds. You don't leave big chunks of the consolidated stuff un broken if there is a chance that inside there might be a diamond that will buy you a new car or a house.

Undoubtedly most of the specimens I have seen in Brazil are fakes, but I have seen some that are undoubtedly real, but like matrix Colombian emeralds there are so many fakes, the the assumption is that almost all of them are fakes. Some people still try to preserve these specimens, and here is a picture of one that is almost certainly natural. The guy who is currently dealing with these has a long track record of honesty with me and he tells me that he has to pay the diggers extra to save a few specimens. He sent me one, not this one, but quite similar, if smaller and I have subjected it to UV, and microscopic examination and I believe it to be genuine and it shows both gold and diamonds in the same speicmen, though neither the diamond or the gold will win any prizes by themselves.

16th Jun 2009 02:50 BSTAlfredo Petrov Manager

Rock, Try soaking it in warm water for a few hours and then poke the matrix immediately around the diamond with a needle. See whether it got soft and plastic. If indeed natural, this test will not hurt your specimen at all. I had 5 that, after studying under the microscope, I would have bet money were all natural, but at least one turned out to be fake (or at least "repaired" ).

We tend to lay too much emphasis on the "reputation of the seller" - meaningless in this context, because even the best sellers get fooled sometimes by their suppliers. For your own peace of mind.... ...and share the results with us. I'm rooting for it to be natural.

Buying directly from miners, at their diggings, is no guarantee either; miners can be an artful bunch. Rock, you've seen the Japan-law twins from the Kami mine, with their characteristic greenish coating of scorodite. I was complaining to the miners once that all the twins they had for sale were loose and busted off the matrix (easy to break off because the point of attachment is so narrow). The next trip, I got nice matrix pieces, on typical scorodite-tinged rock. Looked quite natural and I was happy to buy them. Until I got home and rinsed the dust off. The twins had been stuck into the matrix with bricklayers' mortar, painted over with greenish grey paint! I guess they could honestly tell me there was no glue ;-))

I'm not "bashing sellers" here. We all get fooled from time to time, and we all need to rely more on actual physical and chemical tests, and less reliance on the "reputation of the seller".

18th Jun 2009 20:48 BSTTim Jokela Jr

I've always been suspicious as hell of diamonds in matrix.

The industry isn't set up to recover such things, and in the places where they're still hand mined, surely the first thing the miner would do is remove the diamond from the waste matrix. Why would they carry a rock around?

Also, you have to ask yourself, what's the value of a small, included loose diamond, and what's the value of that diamond on matrix? That's what you call a nice little margin of profit right there.

So I remain highly dubious.

18th Jun 2009 21:47 BSTGuy Kronz

Hi all,

Four years ago I visited the Diamantina region with two friends, but no trace of Diamonds ;).The samples that a local dealer showed to us, where obviously glued diamonds on the local matrix. If there's even some gold with it, the sample is highly doubtful. There are still some people that are working some diamond prospects in the area of Diamantina, but I never heard of some production. What can still be found are the so called quasi-quasi, a very clear quartz in conglomerate matrix.

All the best


26th Jan 2011 19:20 GMTPaul De Bondt Manager

Hi all,

I remember seeing one in the Munich display about Brazil this year.

Didn't take a pic because the room was overcrowded.

I am sure that the show organiser took their precautions before displaying a ( probably ) fake specimen.

Just my 2 cent.

Take care and best regards.


26th Jan 2011 21:13 GMTGerhard Brandstetter Expert

i bought it from a local market in minas gerais. soaked it in water, used uv & my microscope of course. no signes of glue - for me it seems to be natural.

what i also know: i have seen some of this type - all from diamantina area in minas gerais and under the microscope no glue visible.

i also have been in chapada diamantina in bahia: never seen a diamond on matrix.... every (illegal) miner told me: not here!

27th Jan 2011 22:59 GMTAnonymous User

I wrote this little snippet a few years back on another site..figured I would add it here for extra info and to maybe help answer some questions. Not sure if it applies to anything here.

We all know diamonds have been found in brazil in quite large qualtities. Many kimberlite occurances have been found but no large scale kimberlite or lamprolite mining has occured yet. is there a reason for this? As I was digesting my turkey last night I decided to read up on diamond mining in brazil..something everyone knows about but doesn't talk to much about. Lets focus on minas Geraes where the largest concentration of doiamonds have been found. Most of you know that most brazilian diamonds have been found or are found in rivers and river valleys. Common knowledge and common sense dictates that these rivers have cut through diamond bearing rock or strata and picked them up and carried them to these river valleys and streams. While most diaomonds are found in these streams they can also be found up on the valleys side walls. What does that mean..well older deposits from when the river was younger and didn't cut so deep into the earth yet....and of course the higher concentrations are in the river as opposed the the sides of the valley due to water action..makes perfect sense. Okay now lets move to the actual diamond bearing or diamond host rock which is the whole reason behind my little paragraph. What scientist have determined is itacolumite is the host. This itacolumite is evidently the source from which the diamonds and the material in which they are found have been derived. Those rivers which flow through strata composed of itacolumite are diamond bearing, while in those flowing through districts from which itacolumite is absent no diamonds are found. The definition of itacolumite is :A variety of sandstone that is flexible when cut into thin slabs. hmm..thats real blue yellow lamprolite dikes??? This itacolumite and also quartzite are what forms the plateaus where the rivers cut through and pick up the diamonds. Now these diamonds are found in these plateaus in assocaitaion with oxides of iron and titanium, tourmaline, and the most important quartz(rock crystal). Now the diamonds are not just scattered about in some random order on these plateaus interspersed throughout this itacolumite and quartzite..they are found in veins which are made up mostly of veins of quartz which are sometimes shot though with fingers of shist. The circumstance that the diamond is invariably associated with these minerals, and with them alone, points to the conclusion that it originated in the mineral-veins. This conclusion receives additional support from the fact that Brazilian diamonds,


"instead of exhibiting a perfect and complete development on all sides such as is characteristic of embedded crystals, frequently show on one side an area by which they seem to have been attached during their growth and development, impressions of quartz-crystals being sometimes seen on such areas of attachment."

Moreover, diamonds have been found enclosed in, or attached to, the surface of crystals of quartz, anatase, and hematite, and this could scarcely be explained except on the supposition that these minerals have all grown together at the same time and in the same vein. That is the key found with impressions of quartz crystals on them and diamonds found attached or even better enclosed in quartz crystals. It has been stated by Claude henry Gorceix that


""a few diamonds have in places been met with actually in the mineral-veins themselves, and, though in small numbers, have been extracted; he compares such occurrences with that of the yellow topaz found near Ouro Preto in quartz-veins penetrating decomposed schists. In these districts, then, the diamond is a vein mineral, while in other localities it is an original constituent of the primitive crystalline rocks."

Let me tell you who Gorceix is before we move on..he was a french mineralogist who founded the school of mines in Ouro Preto and he studied these depostis pretty extensively. Okay so where were we...Although no diamond has ever been found actually in a quartz-vein, yet the minerals associated with it occur in such situations with great frequency, and their constant association with the diamond, not only here but at all other localities of Minas Geraes, seems to point to a common origin for both. The fact that the diamond itself has never been found in a quartz-vein may perhaps be explained by the extreme rarity of its occurrence as compared with that of other minerals. The clays in which the diamnd lies, are decomposition products of the rocks which were originally penetrated by the quartz-veins. So where does thias bring us? A prehistoric sedimentary deposit maybe..that was subject to low temperature and pressue metamorphism then shot through with quartz veins and schist? that would seem to be the more plausible explaination since we all know diamonds form at high temperatures and pressures and would never even think abpout forming at the same levels as quartz or hematite crystals. That would be my best guess..old paleo placer deposits like those in guyana and venezuela that have been intruded with quartz and schist veins which happened to come into contact with quartz crystals, hematite, and the other associated minerals. Very odd diamond occurance indeed..any thoughts?



28th Jan 2011 00:09 GMTAlfredo Petrov Manager

Jason, the association of diamonds with quartz in placers and metasedimentary quartz-bearing rocks is just coincidental and doesn't imply any relationship in their primary paragenesis. Another almost universal association in placers is lead fragments from bullets and shot - No genetic association!

As for quartz crystal impressions in diamond, without photographic evidence, or better yet a physical specimen deposited in a museum, it will be hard to convince a mineralogist that this is any more than a rumor. Ditto for Gorceix's comments about diamonds in "mineral veins" - As a mineralogist, he should have deposited specimens in a responsibly curated museum, without which most will tend to remain sceptical.

28th Jan 2011 04:43 GMTAnonymous User

I titled the write-up "No kimberlite or lamprolite here" which i forgot to include

I agree with all you said above.

25th Sep 2017 03:31 BSTNorman King Expert

This discussion inspired me to write an article on distinguishing real from fake diamonds in conglomerate, published today. My discussion is based largely upon a specimen from Brazil that I recently acquired from Jack Crowley of The Crystal Mine. This specimen also passed through the hands of Jewel Tunnel Imports (Rock Currier). Obviously, there is too much in the article to duplicate here, so I refer you to "My Specimen of Diamond in Conglomerate From Brazil: Real or Fake?" at: Photos are also at, but I shortened the description there, also referring browsers to the article.
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