The chemical composition ranges from Pt2.64Fe1.00 to Pt2.88Fe1.00 with Os, Ru, Ir, Rh and Pd below the analytical detection limit of the electron microprobe.
That means they didn't detect any, but do not want to commit to claiming it's pure.
Or, it could mean that they detected some but it's < 0.1% so they can't throw any numbers up. As I said, additional information is required to tell one way or the other. It'd sure help if someone could get access to the entire article, not just the abstract... (I live half an hour away from my university, so I might drive in on the weekend and browse the library. At the very least, I'll have free access to several academic networks from there.)
Oh, by the way I've updated the OP.
"below the analytical detection limit of the electron microprobe" pretty much says that they didn't find impurities using the electron microscope. "below the analytical detection limit" is the same as "nothing above the analytical detection limit", being "above the analytical detection limit" is a prerequisite for detecting the impurities. Since it is an electron microprobe, there is really nothing purer than the sample they described.
Actually, that source is not contradictory, it only seems so due to a misinterpretation of the meaning of the word "native". Read the very next sentence:
Platinum is usually alloyed with several per cent of iron and with smaller amounts of iridium, osmium, etc.
So this just confirmed that the so-called "Ferroan Platinum" does indeed contain other platinum-group metals. These impurities make the metal to brittle to work with and they cannot be removed with heat alone. It takes a complex chemical process to do so.
So, unless you suspect that DF smelting technology includes massive chemical vats and temperatures far exceeding those of molten rock, then it is completely unrealistic that dwarves would be able to purify native platinum into something malleable.
I don't think every metal in the game comes out of the ground 100% pure. Also, naturally occurring alloys change depending on where they are dug up in the world. Just because alluvial deposits in the USA contain x% of iron doesn't mean some cluster in South Africa, nor under my mountain-home, should do too. There is no standard, because nature doesn't have one. Hence the hand-waving with the numbers in reality and in the game. If you add even a sparing amount of fantasy-hand-waving on top of this, like an extra 200 degrees to a dwarven-smithy's forge, some extra chemicals he adds on his father's advice, I really don't see a problem.
"As a result, platinum is often found chemically uncombined as native platinum. "
http://en.wikipedia.org/wiki/Platinum I don't know if someone is changing the wikipedia article back and forth since it is user editable so i'll add another source.
"The platinum metals are often found together in nature. In fact, one of the problems in producing platinum is finding a way of separating it from the other platinum metals. Unlike gold, however, these metals do not occur in masses large enough to mine."
http://www.encyclopedia.com/topic/platinum.aspx which happens to contradict it. "Platinum is also used in small amounts in alloys. For example, cobalt alloyed with platinum makes a powerful magnet. An alloy is made by melting and mixing two or more metals. The mixture has properties different from those of the individual metals. The platinum-cobalt magnet is one of the strongest magnets known." "The ordinary variety of native platinum is called polyxene; it is 80 percent to 90 percent platinum, with 3 percent to 11 percent iron, plus the other platinum metals, and gold, copper, and nickel."
http://www.britannica.com/EBchecked/topic/464081/platinum-Pt This would make a good model for your "platina"
And yes that research does contradict that platinum can be found in pure form in nature, but I already linked to where you could buy a "pure" platinum nugget. No metal ore is truly pure, not even native gold, but when it comes out of the ground so pure you cannot detect it's impurities with an electron microprobe it is already purer than any form of smelting could make it.
To summarise; just because platinum is by and large extracted from relatively impure desposits does not mean that purer desposits couldn't be nor haven't been found.
The point is if they have been found, all my research has yet to turn up a record of it. And since I have found several sources stating that platinum never occurs naturally in pure form, that's what I'm going with. The only trick is figuring out if any of the impure forms would be processable by dwarven science. I've ruled out deposits with other PGMs (besides possibly palladium) so the only viable lead now is on "Ferroan Platinum", but I've been too busy lately to chase it. I'll get back on the case eventually, I hope.
As for what could be found... For all we know, there could vast fields of pure platinum and native aluminum along with diamonds the size of soccer balls or even naturally-formed buckyballs down near the mohorovicic discontinuity, far deeper than even the deepest modern mineshaft. Does that mean we should model every theoretical possibility?
Pardon my catching up, I hadn't been on for a while. I like the alchemy idea, and maybe with a research(tech tree) for the fortress.
"And since I
have found several sources stating that platinum never occurs naturally in pure form"
Do you put your trust in articles you read from the web, or mineralogists actually reporting(and selling) nuggets of the pure metal? While no metal is 100.00~0% pure there is a set standard by which a precious metal must meet before it can be called pure.
Also the articles are being misread. Example being "Platinum is usually alloyed with several per cent of iron and with smaller amounts of iridium, osmium" does not mean that "All Platinum nuggets contain Iron, iridium, and osmium". Native Platinum is not the same mineral as IridPlatinum, Ferroan Platinum, or Polyxene in the same way that Native Silver is not the same mineral as Horn Silver, or Tetrahedrite.
Placer Deposits contain Platinum with the other Platinum Group Elements, and sometimes Gold and Silver, and usually not any Iron. Polyxene is the most common type of platinum discovered in a placer deposit, IridPlatinum is another.
Ferroan Platinum does not occur in a placer deposit, it is found in the same environment as iron ores, that's because it is an iron ore with Platinum added. It can be mostly Platinum or mostly Iron, it may contain trace impurities, but it can also be almost pure Iron/Platinum the purity attested to by an electron microscope not being able to detect any iridium/osmium. I admit it is an assumption that impurities that cannot be discovered with an electron microprobe will not affect the crystal structure of the rest of the platinum in the nuggets; However that would also hold true for every metal in the game. Also there is another FerroPlatinum ore FerroPlatinum being the name of a group the two belong to.
That doesn't mean there isn't a place for "Platina" in the game as Native Platinum is indeed extremely rare. So rare that one would have to introduce many unsmeltable stones to the same environment. or maybe make those stones useable with your alchemy system.
EDIT:
I just remembered Toady removed Native Platinum from the game once before, when he removed its environment - alluvial deposits. One of the reasons it's not so rare in the game now is he added it back in to enviroments it doesn't occur in. During that time I modded in Alluvium, Eluvium, Fluvium, and Tillite as pseudo-minerals that Native Platinum could occur in.
The reason I brought that up is that Alluvium and Eluvium count as placer deposits, while Fluvium and Tillite count as secondary deposits. Native Platinum can be made to occur in Fluvium and Tillite Veins, while "Platina"
or Polyxene and IridPlatinum could be made to occur in Alluvium and Eluvium veins or layers; and removed from every other place they occur in the game.