In Simple terms a Jyotish Gemstone or an Astrological Gemstone is a Gem recommended on basis of sacred Astrological principles of Jyotisha to bring in dawn of fame and fortune and accomplishment of desires. But not every Gem is a Jyotish Gemstone. 

According to ancient texts, Rudraksha are very influential in removing malefic effects of the planets. Gems are used specially for enhancing the strong planets . But they are unable to pacify the evil influence hence it is most advisable to wear Rudraksha. Then not only planets are pacified but peace, harmony, good health and abundance comes to its wearer and he becomes a favorite of Lord Shiva. Therefore a man must know which Rudraksha will be useful to him.

The analysis of a birth chart brings to light the weakness and/or afflictions of planets in the birth chart. Such planetary weaknesses and afflictions make the person vulnerable to setbacks in life through mental stress and physical pain. Kavach is prepared to reduce the impact of transit afflictions to weak planets and to enhance the results of the weak planets.