The eleventh Foundation Stone of New Jerusalem.

Jacinth is a semi-precious stone that is also known as hyacinth. It is a lustrous orange-yellow, orange-red, yellow, or yellow-brown type of zircon. Zircon has been prized since antiquity. Zircon's brilliant and intense fire surpasses that of even the diamond. Pure zircon appears colorless and is often used in place of diamonds. Impurities within the stone produce a variety of colors. The name probably comes from the Persian word ‘zargun’ which means ‘gold-colored’, although zircon comes in a wide range of different colors. Deposits can be found in Cambodia, Burma, Thailand, Sri Lanka, Australia, Tanzania and France.

Jacinth or hyacinth comes from the Greek ‘huakinthos’. Most scholars agree that the biblical reference in Revelation was some kind of blue stone, taking its color from the flower. Elder Pliny (AD 23-69) describes the hyacinth as being very different from amethyst, "though partaking of a color that closely borders upon it" and as being of a more diluted violet. It is held that the jacinth/hyacinth could possibly be the sapphire of today, since in biblical times sapphire was thought to be a form of jacinth.

Amulets containing jacinth were thought to protect travelers against the plague and any wounds or injuries they would otherwise experience during their trip. The stone was also thought to insure a warm reception at any inn he visited along the way and even protect the wearer from being hit by lightning. It is believed it will provide the wearer with wisdom, honor and riches; however, if the stone loses luster it is said to warn of danger. Hindu poets tell of the Kalpa Tree, the ultimate gift to the gods, which was a glowing tree covered with gemstone fruit and leaves of zircon. Zircon has long had a supporting role to more well-known gemstones, often stepping in as an understudy when they were unavailable. In the middle ages, zircon was said to aid sleep, bring prosperity, and promote honor and wisdom in its owner.

One of the earliest writers to associate with the apostles the symbolism of the gems given in Revelations is by Andreas, bishop of Caesurae. He gives a brief description of the stones, which is recounted in George F. Kunz's book ‘The Curious Lore of Precious Stones’ (1913). The jacinth, which is of a celestial hue, signifies Simon.