AMULETS - PRECIOUS STONES - GEMS - OPAL Hand-coloured wood-engraving from Johananis de Cuba, Hortus Sanitatis, 1483. The illustration depicts the Orphanus, set by jewellers in the imperial Crown of the Holy Roman Emperor. It is said to have been a particularly beautiful and miraculous large Opal, which (according to Albertus Magnus, in Opera Omnia, V, f.42) formerly had the power to shine in dark. However, if this had been an Opal, none of the specific qualities of this stone were attributed to it. According to the gemmologists, the opal had the power to make the wearer invisible, which is why it was sometimes called patronus forum, or patron of thieves.