banded agate nodule specimen
Agate is, and has always been, among the most popular precious stones. It was first mentioned in writing by the Greek philosopher, surgeon and natural scientist, Theophrastus (376 – 287 BC), but of course, the stone was known and used long before that.
As agate is so conspicuous and brightly coloured, it is understandable that it was one of the earliest stones to be noticed. It was widely used by the ancient Sumerians and Egyptians. Practically every culture of ancient times used agate not only for ornamental purposes and for making a variety of vessels, but also for making all sorts of amulets. The famous cameos and gems were carved from agate and so were beautifully engraved decorative articles, which were highly valued. Agates are most suitable for this purpose, for their variance of colour and unrepeatable pattern ensure originality when used as a precious stone. The earliest agate gems usually represented various symbols. As the occurrence of these most beautiful natural stones is so very rare, it is no wonder that their presence was considered something extraordinary, and even that it was caused by supernatural powers.
info from minerals.net