If you train martial arts high enough , preferably maxed, you can break space rocks on the those twin brick breaking board things you buy at China. After you have broken about 250 (from what I remember) of any type of board above the easiest ones, you start to get gems while breaking space rocks. I get soul stones, tiberium and many pink diamonds that way really easily and efficiently. Worth a try in my opinion.
Definitely agree! The rate you get a Rainbow gem or Pink Diamond is the same as the rate you get a Turquoise or Topaz - basically much greater success of gems than just waiting for one or two spawns over several days. Of course, your sim would have to be high level martial arts (level 10 actually isn't required; I had a sim break a space rock and get a gem at level 7) and have broken 150 (I remember it as 150... but maybe 250 is right) boards of oak or harder material. Then you can break space rocks for gems.
Most optimal is a sim with LTRs like Steel Bladder and Hardly Hungry, and a sim who has done strength work-out for at least 60hrs so they won't ever get exhausted. You can just have the sim break space rocks all day and take breaks for needs, and then get back to work again. You'll get a lot of valuable gems that way.
Myself, I think finding Pink Diamonds out in the wild is too much trouble when most of my sim families have at least 1 Martial Arts master in the house. You don't have to worry about when and where the gem spawns, getting there quickly, collecting it and then going home again. You just have to keep breaking those rocks.
Now, if only the board breaker also could give you metals and I'd never have to worry about those spawns again.