In the case of the stones, they found that every stone emits a vibration that is unique to them. They have no clue as to how this vibration effects the human body, but this 'energy' is often what is considered useful to spiritual people. Also, often the properties of the stones are related to the colour it has, and therefore, when you look at the study of colours done by scientists, it has been noted that certain stones have a certain effect on the human mind.
You know, since I first heard of and studied String Theory, it seems I see the idea of these 'vibrations' everywhere. It makes sense. Each stone has a different make-up, with different 'materials', which are made up of different elements, etc, etc. It seems obvious that the 'vibration' would be different for each.
I believe this happens with people too. Some people seem to 'vibrate' on the same wave length, and I think these are the people we're drawn to.
If a person is tuned into these vibrations moreso than another for whatever reason, I don't doubt the possibility that they could 'feel' the essense of another person.
I may as well throw this out there. I relate to the 'keeping the ability close to the chest' comments. I've had a few experiences myself that I can't really explain and when I voice them they seem as if I were making it up, but I know in my heart how it happened. My last experience was when I'd found a book called Practical Intuition by Laura Day. I'd picked it up at the library thinking there might be some interesting MBTI related stuff in it dealing with intuition and gut instincts... and what it turned out to be was a 'training manual' on how to teach yourself to be more sensitive to these kinds of 'extra sensory' things.
Out of curiousity, I began reading through it and working the exersizes. I was about 3/4 of the way through, and had not seen anything extraordinary yet, but its a short book so I was determined to see it through. I came to an exersize whose results scared the crap out of me. I was shaken so much that I never picked up the book again. Essentially the book tells you to run a free-form writing piece, jotting down things that cross your mind... like a stream of consciousness exersize. Then you go back through it and pick out things that seem to appear as a 'theme' within the paragraph. It can be redundent letter sounds, colors, ideas or phrases... whatever strikes you as important about the paragraph. You write down those important things that you see and that is supposed to help lead you to the answer.
In this instance, I had all but spelled out the answer that was given on the next page, and I SWEAR I never looked. Out of a babbling stream of nonsense from noting how I heard the fan, noticed the neighbor coming home, the red lion on a grocery bag... all utter NONSENSE... I had gone back through it and picked out the answer on the next page and written it at the bottom of the paper I was writing on, and it wasn't something common that could be guessed. It was names of horses who had competed in a race many years ago, and you had to try to determine what the name of the horse was who'd won the race.
Its all about wording though when asking the questions... and before writing I had said 'Hell I'd be impressed if I got close to even ANY of the horse names in the list'... and so when I was done, not only did I have the name (minus one letter) of a horse, but I had nearly come up with three other names in the list as well. (And don't be thinking they were common horse names that anyone could have come up with. I promise you, it was bizarre) I had asked the question wrong. I didn't write to find a WINNER of the race... I wrote to find a participant in the race, and came back with a bunch of them.
Moral of the story... I don't doubt that there are people who can tune in to these kinds of things. That isn't the only instance I've had like that, but it is the one that scared me the most.