304 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



The occurrence of chrysoberjl in the gold-washings of the Sanarka river, in the country 

 of the Orenburg Cossacks in the Southern Urals is very similar to that in Minas Novas, 

 but is quite insignificant commercially. The mineral here is, as a rule, of a fine sulphur- 

 yellow colour, rarely greyish or greenish, and is associated with euclase, rose-red topaz, and 

 other minerals. It occurs almost invariably in very small pebbles, and is accompanied by a 

 small amount of alexandrite, another variety of chrysoberyl. 



Most of the chrysoberyl now cut for gems comes from Ceylon, and is of the chatoyant 

 variety. As these stones are frequently referred to in descriptions of the precious stones of 

 Ceylon simply as cafs-eye, it is often impossible to decide whether chrysoberyl or the variety 

 of quartz, also known as cafs-eye, is meant. It seems that both the chatoyant and the 

 transparent varieties of chrysoberyl are more abundantly found now than formerly, probably 

 as a consequence of an increased demand and a more exhaustive search. Among the finest 

 specimens of chrysoberyl, deep golden-yellow, pale yellow, yellowish-green, greyish-green, 

 dark green, greenish-brown, and other colours, may be seen, with or without the chatoyant 

 effect. Dark green stones show many of the characters, and specially the marked dichroism 

 of alexandrite, a variety of chrysoberyl which will be described in detail below. The largest 

 chrysoberyl-cafs-eye hitherto known came from Ceylon, and until the year 1815 adorned 

 the crown of the King of Kandy ; the other of the two large stones mentioned above was 

 probably also found in this island. 



The stones found in Ceylon vary in weight between 1 and 100 carats, and are found 

 accompanying sapphire in the gem-gravels ; the principal localities are in the district of 

 Saffragam and the neighbourhood of Matura in the south of the island. 



Burma (Pegu) has also been given as a locality for chrysoberyl, but its occurrence here 

 is not a well-established fact. Although the mineral undoubtedly occurs both in India and 

 rather more abundantly in the diamond- washings of Borneo, yet in neither country is the 

 occurrence of any commercial value. 



The tendency amongst jewellers to confuse chrysoberyl with chrysolite (olivine) has been 

 already remarked. This confusion is only possible, however, in the case of specimens of 

 chrysoberyl from which chatoyancy, which is never seen in chrysolite, is absent. The two 

 minerals differ too in their physical characters ; thus chrysolite, with a hardness between 6| 

 and 7, is much softer than chrysoberyl. Again, the specific gravity of chrysolite varies from 

 S'Si to 3'37, while that of chrysoberyl lies between 3"65 and 3'75, so that although both 

 minerals sink in methylene iodide, in the heaviest liquid (No. 1), the former will float and 

 the latter sink. Unless examined in some detail the optical characters give little help in 

 distinguishing these two minerals. 



Chrysoberyl-cafs-eye may also be mistaken for quartz-caf s-eye, and vice versd, in spite 

 -of the fact that the former is usually more brilliant and finer in every way than the latter. 

 Here, again, a difference in the hardness and specific gravity comes to our aid, the hardness 

 of quartz being only 7 and its specific gravity 2"65. Thus, while quartz-caf s-eye floats in 

 methylene iodide chrysoberyl-cafs-eye quickly sinks. 



ALEXATTDRITE. 



Alexandrite (Plate XII., Figs. 8 and 9) is the name given to that variety of chryso- 

 beryl the colour of which varies between dark grass-green and emerald-gi'een. The colour 

 is probably due to the presence of a small amount of chromic oxide. Alexandrite differs 

 from ordinary chrysoberyl also in the fact that it is very strongly dichroic, a crystal or cut 

 stone appearing, when viewed in a direction perpendicular to the broad striated face, not 



