Platinum alloyed with Cobalt, thoughts?

[estro613]

So after choosing my diamond (AVC) at GOG I settled on a setting designed by Ritani. After reading here and gaining some information on the different types of platinum, I e-maied Ritani to see what alloy they use with their platinum. Their response was: 950 Platinum mixed with Cobalt. After doing some quick readings I was under the impression that Cobalt was one of the least desirable alloys. Is this true? What differences will I notice because of the Cobalt as opposed to the alternative alloys.

Let me add, based on what I payed I was disappointed to hear that they use Cobalt, can anyone help me out here with their knowledge!? Thanks.

 

[stone-cold11]

Pt/Cobalt alloy is one of the hardest alloy around, but also magnetic in nature and not a PGM metal like most other Pt alloy

 

[estro613]

What does PGM mean? I''m sorry.

 

[oldminer]

Likely as not, you'll notice no difference from any other platinum alloy product. However, I am told that the cobalt alloy is a bit darker color than the palladium ruthenium or iridium alloyed versions. I really can't confirm this from personal experience. I really don't see much practical difference.

However, if you ever need work done on the ring, you need to inform the jeweler of the cobalt alloy as it is not compatible with other platinum alloys or many platinum solders which are not cobalt alloy based. One needs to keep using the same alloy in repair functions. It isn't a big deal, but it is something I understand that may eventually impact your choice. Otherwise, I don't think you'll have any problem.

 

[stone-cold11]

Some reading. PGM = Platinum Group Metals, metals with similar properties to Pt, relatively inert for example.
http://www.ganoksin.com/borisat/nenam/jewelry-platinum-alloy.htm

Probably the flow characteristics is why Ritani uses it.

 

[Laila619]

Actually Cobalt and Ruthenium alloys are among the best and hardest alloys for Platinum. The one that is too soft is Iridium. Ritani knows what they are doing.

 

[Laila619]

http://www.auenterprises.com/platinum-durability.htm

As you can see, Plat with Cobalt is the hardest.

Platinum 900 Iridium 110HV* 55,000PSI

Platinum 950 Iridium 80HV 40,000PSI

Platinum 950 Cobalt 135HV 64,000PSI

Platinum 950 Ruthenium 130HV 66,000PSI