These correspondences are based on the Western system of Astrology and European gem lore*. The dates below are from the Western zodiac and European times, you could use my suggestions for Sidereal Astrology but the stones ive chosen are not traditional Vedic associations so please consult a Vedic astrologer for a better guide to those.
Here is a list of all the pages ive created of Men's Jewellery for each Sun Sign, just click the links below and take a look (Ill be gradually updating these in 2013 for the new designs):-
The Aries Man ( March 21st - April 20th* )
The Taurus Man ( April 21st - May 21st* )
The Gemini Man ( May 22 - June 21* )
The Cancer Man ( June 22nd - July 22nd* )
The Leo Man ( July 23rd - August 21st* )
The Virgo Man ( August 22nd - September 23rd* )
The Libra Man ( September 24 - October 23rd* )
The Scorpio Man ( October 24th - November 22nd* )
The Saggitarius Man ( November 23rd - December 22nd )
The Capricorn Man ( December 23rd - January 20th* )
The Aquarius Man ( January 21st - February 19th* )
The Pisces Man ( February 20th - March 20th* )
* Please note that dates are aproximate guides, and may be a day off to what you are used to in your part of the world. Your birth sign is based on your location at birth and the Sun moves into the signs at different times from year to year.
Also if you are born on the cusp, which is on the last or first day of any sign above you should generate a birthchart using place and time of birth to make sure which Sun Sign you fall under.
You can use highly accurate and free software like that on astro.com or see a proffesional Astrologer.