Gems Notes and Extracts Augusto Castellani, Mrs. John Brogden 1871

CALCEDONY. 49white ;when broken, the interior has a pearly reflection,slightly translucent at the sharp edges. Harderthan the opal, this substance takes a good polish ; it isunaltered under the action of the blow-pipe, and itsspecific weightis 2'2.The cacholongis found in separate bits in the riversof Bokhara, in the Feroe Islands, in Iceland, in trapprocks, and in Greenland. It is also procured in France ;and in Champigny, near Paris, it is brought from thecaves of calcareous breccia, and some of it is hard, ofbright cleavage, whilst others are light, rough to thetouch of the tongue, and soft as chalk, and thereforeof inferior quality, and to be regarded as imperfectlyformed.There is a variety of this stone called striped, comingfrom Feroe and Ireland, which being composed of thinstrata of white and opaque opals over strata of calcedony,often bluish or greenish, makes very finecameos. Italian artists call it French stone.XVIII.CALCEDONY.THIS hard stone is thus named from the province ofCalcedony, in Asia Minor, whence, in ancient times, itwas procured in great quantities. It is a variety ofagate quartz, generally of a milky- white colour, sometimesbluish ;and this last tint somewhat increases itsvalue.