Coral

Today, another dip into Aberdeen University's Bestiary written and illuminated in England around 1200 AD.
A Bestiary is a collection of short descriptions about all sorts of animals, real and imaginary, birds and even rocks, accompanied by a moralising explanation. Although it deals with the natural world it was never meant to be a scientific text and should not be read as such. Some observations may be quite accurate but they are given the same weight as totally fabulous accounts. This what the Aberdeen Bestiary has to say about coral in the section on the properties of various stones:

Coral grows like a tree in the sea, at which time it is green; afterwards, however, it hardens and takes on a reddish colour. It resembles the branch of a tree. Its virtue is that it drives away lightning and storms, wherever it is; and if it is scattered around a vineyard or olive-grove, or on a field or on seeded ground, it protects it from hail and storms and it increases its yield. It banishes apparitions and brings a good outcome to legal business.