268 QUARTZ FAMILY. 7. Jasper-Agate. Jasper-agate is a mixture of calcedony, or hornstone, and jasper. 1 he jasper is of a red, yellow, or brown colour, and is the predominating ingredient in the agate It oc curs in veins, which sometimes contain ores of different kinds, as ores of silver and iron. The following are less important kinds of agate: 1. Spotted Agate. In this beautiful agate, spots of red, yellow, or brown jasper, are dispersed through a calcedonic base. The St Stephen stone, already described under the article Cal cedony, may be considered as a spotted agate. 2. Clouded Agate. It is so named from its clouded appearance: the cloud ed delineations are of jasper. 3. Star-Agale.. This is an agate with stellular markings. 4. Petrifaction-A gate. This agate contains petrifactions of marine animal sub stances, as shells of the turbinites and tubulites tribes. Geognostic Situation. Agates, as already mentioned, occur in veins in gneiss* and in porphyry, and in balls in amygdaloid. They so occur in porphyritic transition cocks, and in balls and veins in floetz porphyry and greenstone; and probably these*
