Blue sapphire should only be worn if a significant increase in Saturn energy is desired. This can be a very good thing for the right people.Fine, top-quality, unheated blue sapphireSaturn is, in my opinion, one of the most misunderstood planets in Jyotish. Many people fear their Saturn mahadasha, or their Sade Sati period (the 7-year transit of Saturn passing over the Moon in one's natal chart), because Saturn has a reputation of being very challenging. Hard work, obstacles, delays, and chronic exhaustion can occur when Saturn is behaving prominently.Capricorn ascendants tend to do really well with blue sapphires. Taurus ascendants do too. Libra, Gemini, and Aquarius ascendants do best with lighter or smaller blue sapphires, as air signs frequently benefit from a gentle dose of grounding energy without too much heaviness attached to it. Virgo ascendants report some negative side effects when wearing blue sapphires, which is why I personally no longer recommend Saturn stones for them.
For all other ascendants, caution should be exercised with blue sapphires. Fire and water signs (Aries, Leo, Sagittarius, Cancer, Scorpio, and Pisces ascendants) should generally not wear blue sapphires, even during a Saturn mahadasha. If it's not safe or appropriate to wear a blue sapphire, meditating regularly and reciting Saturn mantras are useful tools to help appease this cold andsteely planet.