492 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



and which in some specimens can be distinctly seen with the aid of a simple lens. 

 Specimens of quartz are frequently met with in which these fibres have been destroyed by 

 weathering, their place being taken by fine, hollow canals, each canal corresponding 

 to a single fibre of asbestos. The whole mass of quartz has in this case therefore 

 a tubular structure, but the optical effect is the same as if the fibres were present. 



The chatoyancy of quartz-cafs-eye is displayed to the best advantage when the 

 stone is cut en cabochon, with a decidedly convex upper surface, and with the flat 

 base parallel to the direction of the enclosed fibres. The rounded surface is then 

 covered by a band of light of greater or less breadth in a direction perpendicular 

 to that of the fibres, the other portions of the surface showing no chatoyancy. As the 

 stone is turned about the band of light travels across its surface, finally disappearing 

 at the edge of the stone as the light reaches a certain incidence. 



The chatoyant band has a lustrous, silky sheen of a yellowish- or bluish-white 

 colour, which has been compared with the shining eye of a cat. The stone is usually 

 cut with a rather elongated oval outline, like that of a coffee-bean (Plate XVIII., 

 Figs. 4a and 6), in such a way that the band of light is coincident with its gi-eatest 

 diameter, thus producing the most favourable effect. The cats'-eyes of finest quality 

 are those in which the chatoyant band is of uniform width, not too broad and very 

 sharply defined. Inferior stones are those in which the band is interrupted, too wide, 

 or possessed of ill-defined margins, so that it does not stand out in sharp contrast 

 with the surrounding portions. Specimens in which the band is replaced by a patch 

 of light are also considered to be of inferior quality. The stones most highly 

 esteemed in Europe at the present time are those of a reddish-brown colour and with 

 a delicate bluish- white sheen. They are worth as much as 50s., though at that 

 price they must be very perfect and of some size. Generally speaking, quartz- 

 cat's-eye, especially inferior material, is worth very little, while oriental cafs-eye, even 

 the poorer qualities, always fetches a high price. 



The finest quartz-cat's-eye is found in India and Ceylon. In this quarter of the world 

 the stone is much admired, especially by the Malays, much more so than in Europe, 

 where its popularity depends upon the vagaries of fashion. The reddish-brown stones 

 are usually stated to come from the mainland of India, and the green and grey speci- 

 mens from Ceylon, but this distribution may not always be quite constant. 



Cat's-eye from India is supposed to come mainly from the Malabar coast, in the 

 south-east, and Quilon and Cochin are mentioned as localities, but these statements 

 are not indisputable, and the mode of occurrence is altogether unknown. Since most 

 of the material reaches Europe in the cut condition it is impossible to decide whether 

 the rough material is found in situ or in loose pebbles. At Ratanpur, in the district 

 of Rajpipla, N.N.E. of Bombay, the stone occurs, together with agate, in the form of 

 pebbles, which are undoubtedly derived from the basaltic rocks — the Deccan traps — 

 of the region. Other localities are given in the vicinity of Madras, and in the valley 

 of the Lower Kistna in the neighbourhood of the Palanatha mountains, north-east of 

 Guntur ; also in Burma a few stones are met with. Generally speaking the occurrence 

 of cafs-eye in the mainland of India is insignificant, and individual stones never exceed 

 two ounces in weight. 



While on the mainland of India quartz-cat's-eye is scarce and oriental cat's-eye, as far 

 as is known at present, is absent, in the island of Ceylon both occur in considerable 

 amount. Quartz-cat''s-eye occurs here in grains or pebbles, rarely larger than a hazel-nut, 

 in the gem-gravels of Saffragam and Matura, which have been derived from the weathering of 



