CHRYSOBERYL (ALEXANDRITE) 305 



green but a fine columbine-red inclined to violet. In ordinary diffused daylight, however, 

 this colour is not perceptible, and the stone appears always of a green colour (Plate XII., 

 Eigs. 8 and 9, a). When suitably cut, then, the same stone which by daylight is green 

 appears in artificial light of a red to violet colour; the alexandrite has therefore been 

 described as an emerald by day and an amethyst by night. To accentuate this peculiar 

 character the stone must be cut of a certain thickness, the difference in colour being much 

 less marked in a stone cut with little depth. A crystal of alexandrite when viewed through 

 the dichroscope in a direction perpendicular to the broad striated face gives an emerald- 

 green and a yellow image ; when the direction is parallel to this face one of the images is red. 



Until comparatively recent times alexandrite was found only in Russia, in the emerald 

 mines on the right bank of the Takovaya, a small stream eighty-five versts (about fifty- 

 seven miles) east of Ekaterinburg in the TJrals, a locality which will be considered in more 

 detail under the description of emerald. The stone is found, together with emerald and 

 many other minerals, embedded in mica-schist, close to the line of contact of this rock with 

 granite. It occurs usually in star-shaped triplets, identical or very similar in form to that 

 shown in Fig. 61 c, and Plate XII., Fig. 8, and consisting of three crystals twinned together. 

 Simple or twin-crystals (Fig. 61, a and b,) are very rare. The triplets often measure as much 

 as 9 centimetres across, and sometimes even more ; they have a tendency to grow together in 

 groups, one such group being found to contain twenty-two large crystals and many small ones 

 of the same kind. The occurrence was accidentally discovered in 1830, on the very day on 

 which the coming of age of the Czarevitch Alexander Nicolajevitch, afterwards Czar Alexan- 

 der II., was celebrated, and the mineral received its name in honour of this personage. The, at 

 first, exclusively Russian occurrence of the stone and the fact that it combines the national 

 military colours, green and red, gives it a peculiar value in the eyes of Russians, by whom it 

 is worn with great pride. Crystals of alexandrite are, as a rule, cloudy and full of fissures, and 

 are therefore unfit for cutting as gem-stones ; they may, however, contain pure and transparent 

 portions free from cracks and markedly dichroic, and it is from such portions that gems are 

 cut. It follows, then, that in Russia, at least, if not elsewhere, where the stone is used but 

 little, much higher prices are demanded for alexandrite than for oi'dinary chrysoberyl. and 

 the more so as the mines at the present day are almost completely exhausted. 



P'or a long time alexandrite was known only at the locality mentioned, then it was 

 found with pebbles of ordinary chrysoberyl and other precious stones in the auriferous sands 

 of the Sanarka river in the southern Urals. 



Still more recently alexandrites have been found in comparative abundance in the 

 gem-gravels of Ceylon. These show the characteristic dichroism of the Uralian stones, 

 while some display, in addition, the chatoyancy of cymophane, a feature never seen in 

 specimens from the Urals. The Ceylonese alexandi'ites are, on the whole, finer than the 

 Uralian, the columbine-red colour seen in artificial light being especially beautiful; the 

 chatoyant stones, moreover, which may be called alexandrite-cat's-eye, are peculiar to this 

 locality. The largest alexandrite yet found in Ceylon weighed 63f carats, and those 

 ordinarily found never weigh less than 4 carats. The large stone just mentioned was cut 

 with double facets (Plate III., Fig. 6), and gave a gem measuring 33 by 32 millimetres at 

 the girdle and with a thickness of 17 millimetres. Its colour by day is grass-green tinged 

 with yellow, and by artificial light a fine raspberry-red. Another beautiful stone from 

 Ceylon weighed 28|-| carats and measured 32 by 16 by 9 millimetres. Its colour by 

 daylight was a fine sap-green with a trace of red, while in candle-light it appeared of a 

 full columbine-red, scarcely distinguishable from a purplish-red Siamese spinel. Localities 

 for alexandrite, other than Ceylon and the Urals, are not at present known. 



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