Moonstone - The Feminine Balancing Crystal For Men has a post about crystals for men:

Crystals and gemstones have often been worn by men as jewelry, or to decorate formal suits to signify their official or regal status in society. In ancient times, polished crystals were embedded on shields for protection during battle. Carved crystal amulets offered protection from enemies and poisoned wine. Today, gem and crystal crafting is still almost exclusively men's work. However, the use of precious metals and gem synthetics has slowly replaced the use of gemstones in popular men's jewelry. The use of crystals for healing and ancient secrets was popularized in the tale of England's King Arthur with his wizard, Merlin, who lived in the Crystal Cave.

There are 10 crystals listed in the post. Here's the piece on Moonstone:

"The Feminine Balancing Crystal". To soften and balance dominant male attributes with some feminine qualities, Moonstone provides for a depth of perception and feelings, discernment, creativity and self-expression

SobrietyStones has a bit more on this quality of moonstone

Some people think that Moonstone is strictly a feminine stone, because it is associated with a woman's monthly cycle. But nurturing, gentle care, and unselfish humanitarian service is not simply a female attribute.

Moonstone can unblock those feelings in both men AND women who are afraid to acknowledge or experience consciously how they feel on a personal and internal level.

This is a great stone for Doctors, Nurses, Technicians, and other Health Care Workers, who sometimes feel they must repress much of what they feel in order to function more effectively, at the expense of gentleness that comes with empathy and compassion.

It will bring emotions and feelings under ones control without becoming hardened to the human suffering they see on a daily basis. 

Moonstone will help achieve a balance between heart and mind without losing the gentleness and caring needed, yet keep it in check to allow you to function effectively.

Some of the other properties of Moonstone from Jewelry-art:

  • Moonstone is worn as an amulet to bring good emotions to the wearer.
  • Moonstone offers protection on land and at sea.
  • Moonstone is a good luck stone.
  • Moonstone enhances intuition, perception and judgement.
  • Moonstone can protect those of a sensitive nature.
  • Moonstone is an excellent stone to use in meditation to understand oneself.
  • Moonstone promotes inspiration.
  • Moonstone brings good fortune.
  • Moonstone can reunite lovers who have quarreled.
  • Moonstone assists in foretelling the future
  • Moonstone is a particularly good gemstone for women.
  • Moonstone brings success in love as well as business matters.
  • Moonstone can be beneficial to men in opening the emotional self.