What does the phrase “gem of a person” mean?

The phrase "gem of a person" is used to describe someone who is incredibly wonderful, precious, and valued, much like a rare and beautiful gemstone. When you refer to someone as a "gem of a person," it means you find them to be exceptionally good-natured, kind, or outstanding in their character and behavior. It's a way of expressing high regard and appreciation for someone's qualities, indicating that they are not only admired but also cherished for their rarity and goodness.