Skyjewel 9.25 Ratti Blue Sapphire - Neelam Gemstone for Shani deva Stone Name : Blue Sapphire Weight Ct. : 8.55 Among all the nine astrological gemstones, Blue Sapphire is the fastest acting gemstone. Among all the nine astrological gemstones, Blue Sapphire is the fastest acting gemstone. Blue Sapphire is the gemstone of Planet Saturn as per Vedic Astrology.