If they have received Shiva mantra as upadesha from their Guru, only then they can wear. Otherwise they can wear Tulasi beads or sphatika (crystal) chain.
Rudrākshi, Bhadrākshi, Chidrākshi are varieties of them. In them are one to nineteen faces. One faced or Ekamukhi Rudrāsha is rarely available. It is available in Nepal, Bhutan and Indonesia. Nepal ones are the best. They are Shiva himself. Swamiji’s māla has 108 Ekamukhi Rudrākshas. Even wearing different faced Rudrākshas has its own restrictions. Wearing Rudrāksha according to one’s constellation or Zodiac sign is good.
For ladies crystal chain is advised because it represents Mother Goddess. It has healing qualities as well.
(Q&A Session, Malaysia, 30 Mar 2001)