Desert patinas - how can you tell if they're real?

Hi
It was raised in another thread that certain dealers have a habit of adding a desert patina to their coins. So my question is - how can you tell a real desert patina from a fake one? My understanding is desert patinas aren't true patinas, just sandy encrustations. This Vabalathus/Aurelian from my collection for example - real desert patina or fake?

 

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Good question, and one I would like to know the answer as well.

 

Me too! I usually avoid buying them, not knowing how to tell real from fake.

 

look at the edge of the coin, most people who dust them forget to do the rim, but do both sides. if the rim has hard sandy deposits on, its a fair bet its real. your coin looks good to me.

 

Personally, I don't think there is a definitive way to tell when the sandy patina is hard (if it is soft, I think it is most likely fake).

The coin you show looks like it has has very hard "crust". My guess is that it is real, but those hard patinas can be created with fine sand/dirt + superglue or some type of glue.

I suggest that if it doesn't come off when you scratch it with your fingernail, just leave it alone. If it comes off with a gentle scratch or is soft, soak it in water/alcohol/acetone to remove whatever gunk someone put on it lest the substance damages your coin or hides/causes active corrosion.

Interesting (alarming) article about cleaning, patinas, tooling, etc: http://www.fontanillecoins.com/tooling.htm

 

I don't collect bronze, so never really dug into the matter. But, I would think a dealer who has an unusual amount of 'desert patina' coins should raise a red flag.

 

I have a few desert patina coins and I love 'em, but I don't think that I'll buy them anymore ...

Hey, maybe they'll be known as dated-coins (kinda like furniture and clothing from the Brady Bunch Era?) ...

=> wide-leg jeans, shag carpet, green fridges and desert-patina coins?!!

 

I personally don't trust any desert patina today due to the prolific quantity of artificial examples. Many are done very poorly and are obvious fakes but it only takes continued experimentation to refine malicious skills.

I wouldn't pay a premium for them and would expect a discount as they are most likely obscuring negative details.

 

Hmm interesting and alarming. Some dealers have a lot of these desert patina coins - especially one located in the UAE, but maybe these really were found in the desert.

 

Well, if it's real desert patina then oxalic acid should take it off.
I realized that's not really helpful

 

I'm no expert, but yours looks real to me. Here are some patently artificial ones described as such in CNG sales. Good on CNG for the disclosure.
http://www.cngcoins.com/Search.aspx...R_TYPE_ID_2=1&SEARCH_IN_CONTAINER_TYPE_ID_4=1

 

Not sure I agree. Some dealers have the bulk of their suppliers in regions such as the middle east, so naturally their coins have desert patina. There is an eBay seller who is perfectly legit who's coins are all sandy.

 

Is it interesting that the CNG group seemed to sell well over estimates just as expected for normal coins? Perhaps the new money in the market simply does not care.

 

I've read that even in locales where a desert patina may occur it is a rare phenomena and not often found naturally. Perhaps that assumption is wrong?

 

I've examined hoards of Nabataeans for instance, hundreds of common coins that had exactly the same dirt patina. Nobody in their right mind would have artificially patinated all those worthless coins. Desert patinas are in fact the norm for coins coming from arid, sandy regions, not rarities - from what I've seen.

The OP coin is natural. Get suspicious when the patina is too perfect and the seller wants big bucks. In fact, the OP coin may be as-found, or poorly cleaned. It has good detail underneath - I would clean it some more if it were mine.

 

The CNG listings are instructive because, as you can see, the doctored coins are either low-grade rarities whose details have been "improved" by tooling and painting, or more common coins with sufficient detail, but painted to highlight the devices - hoping for more eye appeal and therefore value. Notice that in either case, the dirt looks carefully placed to do its work, and that it is applied with an even, smooth texture.

A natural "desert patina" will look more like the OP coin - clumpy and randomly distributed. Now you might think this could also be an artifice, but when you've looked through bags of hundred of these coins that look exactly the same (as I have), you begin to realize that this is just how they come out of certain locations.

 

Here's one in my collection that is suspect. I haven't looked at it under magnification.

 

Such earthen patinas are very common to certain regions as has been pointed out, primarily the Middle East. With some experience and study it can be easy to spot. The applied ones often are too smooth, just a 'smear' to bring out and highlight the details. Greg, yours is just fine. You will note that in your coin there are cleaning scratches going deep into the patina. A fake one would be smoother and many look as if the patina is chipping off in places.

 

i think this coin is ok, but i'm suspicious of it's patina a bit...




i learned about fake desert patinas within days of purchasing this coin.

 

Im sure I might have a couple that have fake sand, but truthfully it's "owell". I am not gonna goto the trouble of testing or taking it off.

I don't go out of my way to buy from dealers who ONLY have sand patina, I find that a ringing bell.