OK, I have all my puzzles done and the gong completed. I have a few questions.
1. I have the ancient mosaic floor cleared off, but do not have level 3 Exploration purchased yet. I thought according to the "manual" you needed that to complete that task...?
2. Now that all the jobs are done (extras, that is), is there any other way to get building points besides fixing huts?
3. Could one of the guru designers tell me on the physics of the game what the probability of that yellow rare pebble is of appearing? I watched the mosaid section of the game exclusively during the entire time it was being cleared and it never appeared (well over 10 hours).

im not a guru designer or a specialist in probability but i "believe" a random variable is created to determine which one be it common, uncommon, or rare will pop up. Then another random variable to determine which one of that series will be the one displayed. That is how i would do it logically i think. And to increase the probability as you research exploration i would use a scale of 1 to 10 so i could make more numbers = to rare and less for the others as i researched the tech levels higher.

I'm not a guru designer either but I think that the rare ones also stay in sight for less time than the uncommon ones, which in turn are visible for less time than the common ones. I spotted a pinkish star shell during my game; it was the last of the shells I needed. By the time I'd found a kid (a couple of seconds) it disappeared. I had to wait for at least 24 hours before I saw it again (and bagged it). Of course, it may have appeared and disappeared when I wasn't looking.

it probably appeared a few seconds before you saw it too ive had that happen to a rare pebble i needed. Makes you scream don't it. I only JUST completed my first set today and my game has been running for 162 hours

Try hitting pause if you see something you don't want to miss. Will this not allow you to find a kid to pick it up before it disappears?

It stops the kid, but not the collectible disappearing. Often it is counter-productive, as your eye is caught by the kid running about and s/he might not be so quickly spotted if static.