agate, agath

[In Ger. achat, agat; Fr. agate; Ital. agata; Lat. achates; Gr. ἀχάτης ( achates ).] 1. Min .: A mineral cla ed by Dana as one of the cryptocrystalline varieties of quartz, some of the other minerals falling under the same category being chalcedony, carnelian, onyx, hornstone, and jasper. Phillips, and the earlier school of mineralogists, had made quartz and chalcedony different minerals, and placed agate under the latter species. The cla ifications differ but little: for Dana defines agate as a variegated chalcedony. He subdivides agates by their colours into those which are banded, those in clouds, and those whose hues are due to visible impurities. Under the first category is reckoned the eyeagate, and under the third the mo -agate, or mocha-stone, and the dendritic agate. Other terins sometimes used are ribbon-agate, brecciated agate, fortification agate, . Of these the most familiar is the fortification agate, or Scotch pebble, found in amygdaloid, and with layers and markings not unlike a fortification. Mo -agate does not, as the name would lead one to infer, contain mo , the appearance of that form of vegetation being produced, in most cases at least, by an infiltration of mineral matter. "The agate (or agath) was in old time of great estimation, but now it is in more request. Found it was first in Sicilie, neare unto a river called also Achates , but afterwards in many other places. "- Holland: Plinie , bk. xxxvii., c. 10. "And the third row a ligure, an agate, and an amethyst." - Exod . xxviii. 19. 2. Art : An instrument used by those who draw gold wire. It is 'so called because there is an agate in the middle of it. 3. An American name for ruby type. agate-jasper, s. [Eng. agate; jasper.] An agate consisting of jasper with veinings and cloudings of chalcedony.