The Sardonyx is a rich red-brown stone, the top part of which is formed of a layer of white Chalcedony, or Sard, through which the lower part of the stone shows as a pale flesh colour; when found without the Sard the stone becomes the Cornelian.
The Sard derives its name from a Greek word meaning flesh, and is the Sardius of the Ancients.
The finest Sardonyx come from India and Arabia, but it is also found in Germany and the Tyrol. It is especially good for engraving upon, having a hard smooth surface capable of taking a high polish, and in ancient cameos the under-stone is generally used to form the ground, the lighter top layer being carved into figures, the different depths of the carving affording variety to the effect. These qualities made it a favourite with the Romans, who believed that the virtue of stones could be increased if suitably engraved, so that the Sardonyx was frequently carved with a figure representing Mars or Hercules to render its wearer fearless and courageous.
It was also believed that in common with Agates this stone had the property of preserving its wearers from infectious complaints and the bites of venomous creatures, particularly from the sting of the scorpion; and that if hung round the neck it would allay pain, give self-control, attract friends, ensure conjugal happiness, and success in legal matters. Also, Camillus Leonardus says, it puts restraint upon those inclined to dissipation and makes a man agreeable as a companion.
The Chrysolite is a very beautiful yellow-green gem which derives its name from two Greek words meaning "golden stone," by which name it is referred to by Pliny. It varies in colour, and although exactly the same stone it bears different names; when of a deep bright green, it is known as Peridot, and when of an olive-green it is called the Olivine. It is one of the softest of the hard stones, being easily scratched by quartz.
The stones are found in Egypt, Ceylon, and Brazil, and specimens have been found in meteorites and the lava of Vesuvius.
The Peridot was much valued by the Ancients, the name signifying in Arabic precious stone, and it was at one time considered of more value than the o diamond. These were the only gems set in transparent form by the Romans who wore them for protection from enchantment and against melancholy and illusion. Marbodus says they should be set in gold (gold being the metal of the Sun) to dispel the vague terrors of the night.
During the Middle Ages these stones were worn for foresight with regard to future events, and for Divine inspiration and eloquence.
The Tourmaline is of comparatively modern origin in Europe as far as its use as a precious stone is concerned. It is very remarkable because of its electrical qualities, for when heated one end will become positive and attract straws or ashes, whilst the other end will be negative and non-attractive.
It is transparent in one direction, but if looked at from another it may be found quite opaque.
It is found in India, Siberia, Brazil, and America, and of all colours and shadings of red, pink, yellow, green, and white; two colours may also exist on the same crystal, which may be green at one end and red at the other. This is probably the stone Pliny describes as the Lychnis, which, being very susceptible to solar influences, attracted small particles of chaff when heated by the sun, and had the power of "dispersing fears and melancholic passions." It was also worn to procure inspiration, to attract favours, and to secure friends.