From the Aberdeen Bestiary Project
The second, that is, the second foundation, that is, the second decoration of the foundation, is sapphire. Its colour is similar to that of a clear sky; struck by the rays of the sun, it sends forth, burning, a flash of lightning, signifying the hope by which we are carried off to heaven; through it we are fired with a love of heavenly things, disdaining love of the present world, so that we can truly say with the apostle: 'Our conversation is in heaven' (Philippians, 3:20); 'I will lay thy foundations with sapphires' (Isaiah, 54:11).
Verse
The image of the sapphire is most fitting for the fingers of kings. It shines in an outstanding way and resembles most a clear sky. The power of nature has endowed it with such honour that it is called sacred and deservedly the gemstone of gemstones.
The sapphire restrains the flow of and blood and kills le felun.
Sapphire is of such virtue that it is called the gemstone of gemstones. In colour, it is like the sky when it is cloudless. It is called serc[t]ites because it is found on the shore of Libya in front of sandbanks. This kind is clear; but a better kind is that found in the land of the Turks, although it is not so clear. Its virtue strengthens him who wears it, preserves his limbs intact, overcomes envy and deception, takes away fear, brings him out of prison, and loosens his bonds. It gets rid of an ulcer and cools you if you are overheated internally. Ground up with milk, it serves as an emollient; it is good for the eyes and for an injury to the tongue, and it takes away a headache. If you wear it, you should behave in a chaste fashion.