In old times, especially the so-called Dark Ages. There were quite a few intelligent,learned men who were called, or called themselves, Alchemists. They experimented. With anything and everything. Different ores; gases, explosives, chemicals.
Just as the modern scientist will keep his research secret until he has made a new discovery, so the old Alchemists kept their secrets.
But neighbours, as neighbours will, were "nosey" as to what was going on. Why did these men have fiercely burning fires? What were these explosions we keep hearing?
"They were actually burning rocks! I caught them at it."
And what did these "experimenters" say in answer to these questions? "We are seeking the Philosophers stone; it turns base metal into gold."
"Oh,that sounds good!" said the peasants,"Carry on with the weird smells, and the noise."
One of the great Alchemists was Sir Isaac Newton. He did a lot more than discover Gravity! He was a very clever and intelligent man. He was not so stupid as to try to get Gold from Lead!
The "stone" is a story.A myth. A legend. It doesn't, and never did, exist.
If the Alchemists were searching for anything it was Knowledge. Enlightenment.
It was the curiosity of the Human spirit; "What would happen if I did this? Or did that?"
It still goes on today! But now it is called "Research". and the Alchemists are now "Scientists".
Does anybody these days really believe in the Philosopher's stone?
Only Harry Potter!