QUARTZ (TIGER-EYE) 493 



granitic rocks. Most of the stones are green in colour, but there are also brownish-red and 

 yellow cat's-eyes. like those found in India, they are cut en cahochon before being placed 

 on the market. A large number are sent to Europe, but many also are kept in the country, 

 as cafs-eye is a favourite ring-stone both in India and Ceylon. The pure olive-green cafs- 

 eye with a narrow, sharply defined band of light is most highly esteemed by the Cingalese, 

 who are extremely proud of the occurrence of cat's-eye in their island and firmly believe that 

 it is found nowhere else. This is of course an unfounded belief, for beside localities already 

 mentioned there are several places in Europe where it occurs, though only in inferior 

 quality. 



In Europe cat's-eye of a pale green colour, but scarcely suitable for cutting, is found 

 with asbestos in small brecciated veins in serpentine at Treseburg in the Harz mountains. 

 Stones of rather better quality occur in the diabase of Hof and other places in the 

 Fichtelgebirge in Bavaria; they are often cut but are much inferior to Indian stones. 

 Cafs-eye of a quality suitable for cutting is not found in Hungary, in spite of the fact 

 that this gem is sometimes referred to by jewellers as " Hungarian cafs-eye." 



In Europe cafs-eye is worn principally in rings, pins, brooches, &c., the small size of 

 the finest Indian and Ceylonese stones, indeed, precluding the possibility of any other 

 application. Larger objects cut from this mineral are rare; as an example may be 

 mentioned a bow] of yellowish-brown cafs-eye in the Vienna treasury measuring 5 inches 

 in length ; the block of rough material from which this was cut must have been of 

 considerable size. 



A stone very similar in appearance to cafs-eye can be obtained by treating tiger-eye 

 with hydrochloric acid. The colouring matter is dissolved out by this treatment, and the 

 greyish material which remains shows when cut the chatoyancy of cafs-eye. Together 

 with the brown cats'-eyes of Ceylon there are sometimes found specimens of satin-spar, a 

 variety of calcite, which show a reflection of milky light very like that of true cafs-eye. 

 This is much softer, however, and in contact with hydrochloric acid it effervesces, while 

 true cafs-eye does not. 



TIGER-EYE. 



Tiger-eye is a variety of quartz with a finely fibrous structure. It ranges in colour 

 from yellow to brown, and when cut and polished in the direction of the fibres exhibits a 

 magnificent golden lustre. A polished piece of tiger-eye is represented in Plate XVIII., 

 T'ig.5. 



The mineral occurs in the form of thin plates or slabs, which are bounded by parallel 

 surfaces, and are rarely more than a few centimetres in thickness. The fibres are arranged 

 parallel with respect to each other and perpendicular to the surface of the plate ; they are 

 not always perfectly straight ; they may be curved, or each may have a sharp bend at a 

 certain place. 



Even on an ordinary fractured surface the silky lustre of the stone is vei'v apparent, and 

 this may be considerably increased by cutting and polishing. A polished surface turned 

 towards the light usually exhibits a series of magnificently lustrous yellow bands, arranged 

 parallel to the surfaces of the original plate. These lustrous yellow bands alternate with 

 dull brown bands, which show little or no silky lustre. A slight change in the position of 

 the stone results in a reversal of these conditions, the dark bands becoming lustrous and the 

 silky yellow bands dark. Every movement of the stone, therefore, is attended by alternations 

 of brightness and dulness in the bands. This constant alternation in the appearance of the 



