Beautiful Moonstone, what are your secrets? I don't know if we'll ever truly figure out everything about her, a lady has to have SOME mysteries, after all. ;)
Seriously though, Moonstone's name is somewhat literal in that she's been linked to multiple moon deities, and in some traditions, was even beleived to be formed from drops of the moon itself. Moonstone is a stone of the emotions and intuition. She has a sensitivity and adaptability to the energies around her, and definitely carries some of that watery nature in the forefront.
Don't make the silly mistake of thinking that because she's sensitive Moonstone's weak. Remember, the moon controls the ocean tides, an inexorable force of nature that nobody can stop, or even do much to divert. Where the moon goes, the water follows regardless of what's in its path.
The sensitivity that Moonstone brings helps us in matters of the heart, letting us better perceive what's going on external to ourselves. Moonstone is also a protective stone, deflecting misfortune and negative influences. She's not real keen on misuse of power, and easily uses her watery nature to deflect incoming missiles whether flung with intent or accidentally.
Moonstone is a powerful ally when we need to have a softer, feminine touch, but still be protected, especially while remaining sensitive to our environment and the people around us. Moonstone knows what's hidden in the dark, and she'll bring it to the surface, becoming a reflection of 'what is' rather than what we may perceive to be.
In that sense, Moonstone is also an excellent stone when needing to uncover the truth about ourselves and/or our situation. She offers no judgement on what she shows us, that's completely on us, she's simply the mirror, helping us to face ourselves.
It's important to note that while known for it, not all Moonstone displays the beautiful adularescence (shimmer and flash) of Rainbow Moonstone. Some Moonstone may hide its nature, appearing only as a simple white or grey stone. After all, drawing attention isn't always the best route.
Whether you're drawn to shimmery Rainbow Moonstone, or more towards the hidden forms of this amazing stone, Moonstone is truly a great stone to work with. She's gentle, but has an underlying strength at the same time, teaching us the lesson that the softest forces are sometimes the strongest.