This section is from the book "Ancient Legends, Mystic Charms, And Superstitions Of Ireland", by Jane Francesca Wilde. Also available from Amazon: Ancient Legends, Mystic Charms, And Superstitions Of Ireland.
The charms by crystals are of great antiquity in Ireland -a mode of divination, no doubt, brought from the East by the early wandering tribes. Many of these stones have been found throughout the country, and are held in great veneration. They are generally globular, and appear to have been originally set in royal sceptres or sacred shrines. A very ancient crystal globe of this kind, with miraculous curative powers, is still to be seen at Currahmore, the seat of the Marquis of Waterford, and it is believed to have been brought from the Holy Land by one of the Le Poers, who had it as a gift from Godfrey de Bouillon. The ball is of rock crystal, a little larger than an orange, and is circled round the middle by a silver band. It is still constantly borrowed by the people to effect cures upon cattle suffering from murrain or other distempers. This is done by placing the ball in a running stream, through which the cattle are driven backwards and forwards many times.
The peasants affirm that the charm never fails in success, and the belief in its miraculous powers is so widespread that people from the most distant parts of Ireland send to Currahmore to borrow it. Even to this day the faith in its magic power continues unabated, and requests for the loan come from every quarter. The Marquis of Waterford leaves it in the care of his steward, and it is freely lent to all comers ; but to the credit of the people it may be noted, that the magic crystal is always brought back to Currahmore with the most scrupulous care.1
1 Extract from a letter by the Marchioness of Waterford, on the Currahmore Crystal.