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

54 GEMS.The carbon of which we speak can be cut intofacets on the mill like the diamond, and,in thatcase, it reflects light while still remaining perfectlyopaque.It is found in great abundance, and therefore can behad for from six to seven lire the carat.Its dust is preferable to that of the diamond, onaccount of its low price,and is found exceedinglysuccessful in engravings on pietra dura and in cuttingcameos.We must not mistake this substance for the adamantinespar of China.THE name of thisXXI.CYANITE.stone comes from the Greek KVO.VOS,blue, which was givenit on account of its colour. Ithas been known in various ages, and there is a traditionthat it was wrought in England,under thereign of James I., by one Cornellius, a German artist,who called it seppara, which name it still retains inFrance.The tint of the cyanite is Prussian blue, and occasionallyit fades from that to grey or green.It does not melt under the blow-pipe. It is transparent,and presents prismatic reflections, especiallywhen cut smooth. Its specific weightis 3*5. It isnot very hard, but scratches glass with its angles.