According to ancient VEDIC Astrology, natural gemstones transmit astral powers like radio crystals transform sound! Fine flawless gems promotes good fortune, while poor gems have the opposite effect. The power of gems emanates from the nine planets(nava-graha) recognised by the ancient Asian, "Sideral science of Astrology".
Gemstones strenghten planetary powers and will boost their specific influences in three ways. First way is by adding 'cosmic color' to one's own aura. The second by 'astrologically' enhancing associated areas of one's life. Third way is by attracting the attention of their ruling planetary deities.
five methods of choosing gemstones :
The first is determined by one's birth 'rasi' or zodiac (Moon) sign.
The Second method is based on one's birth constellation or 'naksatra'.
The third choice is based on one's lagna or 'rising sun'.
The forth way to choose one's planetary gem is based on prefrences. If a person is attracted to the influence of a particular stone, and provided it is'nt a dangerous planetary gem or harmful in their horoscope then one can use the gem for one's liking.
The fifth and most specific method is based on the prescription of a qualified 'Astrologer'. The astrologer on the basis of birth horoscope studies the position of nine planets. And determine which planet(s) would be most benefecial to strengthen. Time periods for using certain gemstones may also be prescribed based on one's Mahadasa or 'major planetary periods', Antardasha or 'sub-periods', as well as other astrological considerations.