Agate Or Achat is a precious stone, partly transparent, and partly opaque; usually diversified with a variety of colours, veins, spots, etc. sometimes exhibiting figures, or appearances of natural objects. There are various kinds of agate, which according to their different colours and degrees of transparency, have different names. The principal are these four, the onyx, the chalcedony, the block, and the German agates. Agates have ordinarily reddish tints, and are of all colours, except bright red, orange and green. They are compounds of chalcedony, carnelian, jasper, hornstone, quartz, amethyst and opal. De Boot mentions one of the size of a nail, wherein a bishop with his mitre was very well represented; and turning it a little, a man and woman's head were seen in its place. The Sardian and
Sardonic agates are very Valuable ; the latter is of a sanguine colour, and is divided into zones, which seem to have been painted by art. Pliny, Strabo, and Cicero, say that Polycrates' ring was a Sardonyx. Authors also speak of Roman agates, Egyptian agates. and others. The ancients mention a red agate spotted with points of gold, found in Candia, and called sacred. Agate has always been esteemed for seals; as being a stone that no wax will stick to. Mr. Boyle takes agate to have been formed of separate beds of strata of tine clay or earth, brought by a petrifying liquor to coagulate into a stone. He mentions an agate With a moveable spot, or cloud in it. No country affords finer agate or in greater abundance than Germany. It is found in great quantity at Oberstein, where several thousand persons are employed in quarrying, sorting, cutting and polishing it.