After being at Hogwarts for only a few months, Harry learns about the existence of the Sorcerer's or Philosopher's Stone, in fact he reads a brief text about it on his chocolate frog card on the Hogwarts Express. We all know that it was Nicholas Flamel that invented this stone, with some assistance from Albus Dumbledore.

What is curious is why Nicholas Flamel decided to create the stone, what purpose did he have in mind?

But, regardless of his purpose in creating the stone, the fact remains that he lived and died in relative obscurity, and the rare mention of the Stone appears on Dumbledore's frog card.

In all of the 7 books, You-Know-Who seek tirelessly for immortality. Even in the times before Harry is born, when Tom Riddle was at Hogwarts school he sought knowledge of horcruxes. Why did he not seek out Nicholas Flamel, or speak of him? He has achieved what Tom Riddle most desires! Why does Riddle-Voldemort not idolise the man or seek advise from this wizard?

I think Dumbledore explains this correctly in HBP. Voldemort didn't like the idea of having to rely on a stone that could break or be tarnished. Also stealing Flamel's stone would only help him for a limited time, to use that solution permanently he would have to learn how to make his own stone and Flamel, who was close to Dumbledore, would be unlikely to do so.

Also, wouldn't having a philosopher's stone still leave Voldemort vulnerable to being killed by an enemy. A stone would prevent death from old age, but would it prevent death from an AK, or some other attack? The horcruxes meant that he wouldn't be really killed even if an enemy attacked and defeated him.

After being at Hogwarts for only a few months, Harry learns about the existence of the Sorcerer's or Philosopher's Stone, in fact he reads a brief text about it on his chocolate frog card on the Hogwarts Express. We all know that it was Nicholas Flamel that invented this stone, with some assistance from Albus Dumbledore.

The Stone is something that alchemists have theorized about for centuries and have endlessly tried to create, so Flamel didnt invent anything, but obviously the actual creation of this stone is not easy.

Why did Nicholas Flamel want to create a Philosophers Stone, and why was he not well known for such a remarkable achievement?

In all of the 7 books, You-Know-Who seek tirelessly for immortality. Even in the times before Harry is born, when Tom Riddle was at Hogwarts school he sought knowledge of horcruxes. Why did he not seek out Nicholas Flamel, or speak of him? He has achieved what Tom Riddle most desires! Why does Riddle-Voldemort not idolise the man or seek advise from this wizard?

A stone would prevent death from old age, but would it prevent death from an AK, or some other attack?

At the time Dumbledore was born, Flamel was over 500 years old. It's highly likely he'd perfected the Stone previously.

Dumbledore was a (nearly) unique talent, a once-in-innumerable-generations power. I imagine Flamel (having endured some tedious centuries with no equal) was glad to find someone he could mentor, to some degree. It's more likely Flamel helped Dumbledore with, say, the uses of dragon's blood than that Dumbledore helped Flamel with the Stone.

What you say is very logical but, looking at the exact wording and order of wording on the chocolate frog card in PS, it really looks like Jo meant to impart the information that Dumbledore and Flamel worked together on alchemy specifically. (The uses of dragon's blood were DD's alone.)

Chapter 13, p. 160, Raincoast:
(Harry): "I've found him! I've found Flamel! I told you I'd read the name somewhere before, I read it on the train coming here - listen to this: 'Professor Dumbledore is particularly famous for his defeat of the dark wizard Grindelwald in 1945, for the discovery of the twelve uses of dragon's blood and his work on alchemy with his partner Nicolas Flamel.'!"

Remember, this is Jo's first book and, in my opinion, this wording was not quite thought out. Why would the great alchemist Nicholas Flamel - as Hermoine says on the next page, "the only known maker of the Philosopher's Stone" -take on a wizard 500 years younger than he as a "partner"? Don't make sense.

I do agree with the poster above that the more logical explanation is that Flamel recognized the genius of the young Albus and chose to mentor him. The author more correctly should not have worded it as she did on the chocolate frog card to make it look like Flamel and Dumbledore were somehow equal in their alchemy accomplishments. Or rather, when it came to the work on the Philosopher's Stone.

"Dumbledore is particularly famous for ... his work on alchemy with his partner Nicolas Flamel." (Chapter Six, p.77, Raincoast) Hmm. His work with his partner on the Philosopher's Stone? Again, couldn't be. But undoubtedly, over the years, the extraordinary Dumbledore did work with his mentor on other alchemy stuff and probably helped him immeasurably in that field. As no other wizard or witch would have been able to.

As I see it.

The best-known goals of the alchemists were the transmutation of common metals into gold (called chrysopoeia) or silver (less well known is plant alchemy, or "spagyric"); the creation of a "panacea", or the elixir of life, a remedy that, it was supposed, would cure all diseases and prolong life indefinitely; and the discovery of a universal solvent.[6] Although these were not the only uses for the discipline, they were the ones most documented and well-known.

The double origin of Alchemy in Greek philosophy as well as in Egyptian and Mesopotamian technology set, from the start, a double approach: the technological, operative one, which Marie-Louise von Franz call extravert, and the mystic, contemplative, psychological one, which von Franz names as introvert. These are not mutually exclusive, but complementary instead, as meditation requires practice in the real world, and conversely.[8]

Several early alchemists, such as Zosimos of Panopolis, are recorded as viewing alchemy as a spiritual discipline, and, in the Middle Ages, metaphysical aspects increasingly came to be viewed as the true foundation of the art.

In his Alchemical Catechism, Paracelsus clearly denotes that his usage of the metals was a symbol:

Q. When the Philosophers speak of gold and silver, from which they extract their matter, are we to suppose that they refer to the vulgar gold and silver?

A. By no means; vulgar silver and gold are dead, while those of the Philosophers are full of life.