An interview is a chance for you to get to know the target company, just as much as it is a change for them to know you.
I hate to say this, but I after a decade in the job industry, I fully understand where the hiring managers are coming from. Big diamonds are just like skulls in the workplace - people see them and make assumptions. Let the person know you are competent before they realize you are posh. There should be a rule for new graduates - never wear more on your person than you will be making in six months at the job.
I know the following statements aren't always true - but they are often assumed.
1) Someone who has nice things probably expects to be paid a living wage, and might negotiate or walk out if I offer them too little.
2) Young people with nice things are brats, because you know they haven't had the time to work for them.
3) People who wear a diamond to work for a company that thinks many diamonds are death and destruction are probably not going to be sensitive to the fact that the Company is Anti-Diamond!!
I have a taste for vintage and a bargain. In addition, I inherited many nice things - I couldn't afford to pay full retail for the items I own and carry. I've heard people gossip about me - and some of that gossip is very malicious. But, I think the fact that I can talk fashion with my boss has resulted in my last raise...