CORUNDUM: OTHER COLOUR-VARIETIES 293 



precious stones ; while the latter sink heavily in the heaviest liquid (sp. gr. = SS) the 

 former float in this, some indeed floating in pure methylene iodide. Very little familiarity 

 with the appearance of "oriental" and "occidental" precious stones enables one to 

 distinguish the former from the latter solely by the difference in lustre ; and this difference 

 has led to the term " oriental," conveying by its use an impression of great hardness and 

 brilliant lustre in the stone to which the term is applied. 



None of the colour-varieties of precious corundum now under consideration are 

 abundant in nature. They occur as more or less isolated examples, together with ruby and 

 sapphire, at the localities where these precious stones are found, namely, in Burma, Siam, 

 Ceylon, Montana, North Carolina, &c. Together with the ruby a,nd sapphire they are 

 collected from the various deposits, and are cut and mounted in the same manner as are 

 these stones, so that further comment on this subject is superfluous. 



" Oriental aquamarine " is pale bluish-green or greenish-blue in colour, and 

 resembles in this respect, and also in transparency, the variety of beryl known as 

 aquamarine. " Oriental aquamarine " sometimes inclines most to green and other times to 

 blue ; specimens are also met with of a dark greenish-blue colour, a transition shade 

 bet^veen the colour of the sapphire and that of the aquamarine. Such stones are remarkable 

 for their specially strong dichroism. 



"Oriental emerald" is corundum of a more or less intense green colour 

 resembling that of the emerald, another colour-variety of beryl. While the "oriental 

 emerald " always shows a tinge of yellow, and is thus inferior to the true emerald in purity 

 and depth of colour, it surpasses the latter in transparency and lustre. So rare is this 

 variety of corundum that its very existence has been doubted, and it has been suggested 

 that the supposed specimens of " oriental emerald " are in reality true emerald or beryl. 

 This idea, however, is negatived by the well-established occurrences of the stone not only in 

 Burma, Siam, and Ceylon, but also in New South Wales, Montana, and at the Culsagee 

 mine in Macon County, North Carolina, where a crystal measuring 100 by 50 by 35 

 millimetres was once found. On account of its great rarity the " oriental emerald " far 

 surpasses in value the finest sapphires, but falls short of the value attached to the ruby. It 

 is distinguished from the true emerald by its greater hardness and specific gravity, and by 

 the fact that it is much more markedly dichroic ; the two colours shown by the dichroscope 

 are blue and green. This variety of corundum sometimes varies in colour according as it is 

 viewed in reflected or transmitted light. Thus a stone from Chantabun, in Siam, appeared 

 in reflected light of a deep bottle-green and in transmitted light of a bluish-violet colour. 



" Oriental chrysolite " is of a pale yellowish-green colour ; its tint is more yellow 

 than that of the last variety of conindum considered, and corresponds very closely to that of 

 chrysolite (olivine) or to pale coloured chrysoberyl. It is much commoner than " oriental 

 emerald." Clear and transparent gi'eenish-yellow chrysoberyl, with no chatoyant lustre, is 

 sometimes referred to as " oriental chrysolite " ; it is distinguished from chrysolite proper 

 by its much greater hardness. 



" Oriental topaz " (" topaz-sapphire," yellow sapphire) is of a pure yellow colour. 

 The value of this stone depends upon the particular shade of its colour ; specimens of a 

 saffi-on-yellow tinged with red or of a pure citron-yellow are most highly prized. In the 

 majority of stones the colour is a pale straw-yellow, or it may incline to green or brown ; in 

 the former case it approaches the colour of " oriental chrysolite." Precious corundum with 

 a more or less pronounced yellow colour is fairly common ; the finely coloured " oriental 

 topaz," however, is much rarer, and being both rarer and more beautiful in colour than 

 "oriental chrysolite" is more highly prized. The price of stones showing great depth and 



