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Platinum Percentage - Weight versus Volume


Steve in Arizona
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Am I correct in my assumption that the platinum alloy in rings marked “950” indicates that the ring’s total weight is a combination of 95% platinum and 5% copper or other metal. Does anyone know what the percentage of the volume of a platinum ring is actually platinum? I am wondering if I am going to be buying a copper ring with a little platinum added for a shiny gray color.

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All of our platinum rings are 100% precious metal. It is usually alloyed with either ruthinium or iridium which are in the platinum family as well. I've never heard of it being alloyed with other metals that are not precious such as titanium. copper etc.

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Steve,

 

It will depend on your alloy. Most 950 platinum in the US is 5% Iridium but I suppose the metalurgist could do it with something else if they really wanted to. Iridium is very slightly denser than platinum (22.16 vs 21.51) so 950 plat/irid alloy would be about 95.1% platinum by volume. Theoretically if they could alloy with something very light, say aluminum, this could get into the 80's but I've never heard of such a thing being done and I can't imagine why anyone would do it other than to just to prove that they could.

 

Neil

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It is usually alloyed with either ruthinium or iridium which are in the platinum family as well.

 

A "platinum family"? This must be a jewelry term. As far as I know, ruthenium and iridium are merely other elements. They are not associated with or derivatives of platinum.

 

I've never heard of it being alloyed with other metals that are not precious such as titanium. copper etc.

 

Which metals are considered "precious"? Again, this must be another term of the industry. I'm just a dumb physicist :)

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Precious metals simply refers to the rarity and economic value of metals.. Plutonium in a "precious" metal but we don't make much jewelry out of it.. And for a bit of history.. At one time aluminum was considered a precious metal until production made it common.. But, general, when people talk of precious metals they are referring to gold, silver, platinum and a few other less common metals..

 

The platinum family of metals is just that.. It's the group VIII (or transition metals) of ruthenium, rhodium, palladium, osmium, iridium, and platinum.. They all have similar physical and chemical properties and tend to occur in the same mineral deposits.. This is the same as refering to the "nobel gasses", "halogens", or any other 'grouping' in the periodic table that shares similar properties..

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