Diamonds are fairly common on Earth. We just have a monopoly controlling the supply to up the prices and controlling advertising to make them seem more important than they should be. I'm not big on them beyond their utility.
I think a lava planet is interesting, plus from Alpha Centauri it's only 5 or so years old, so hey. If it's earth sized though, one might infer its still forming to some degree. When we get better scopes (Or find a way to beat the no FTL rule without costing buckets of energy), might be a worthwhile study object. Unless it's under the gravitational tidal forces of the suns, then it's lava like Io is.