AMBER 539 



slightly different from that of amber itself. Light is thus enabled to pass through the mass 

 of amber without hindrance and the substance appears in consequence clear and transparent. 

 If the oil is mixed with some colouring matter, this also penetrates the amber and imparts 

 its colour to it. 



Unless the greatest care be taken the operation of clarifying amber results in the 

 development of peculiar cracks, which in some aspects resemble fishes' scales. These are at 

 first so small as to be scarcely noticeable, but gradually become more and more conspicuous 

 and begin to show iridescent colours, until towards the end of the operation they become 

 quite obvious as shining, golden cracks. These are known to the amber workers as " sun- 

 spangles," and their presence often serves to distinguish a clarified from a naturally 

 transparent specimen of amber. 



Having dealt with the yellow varieties of amber in some detail, we may now briefly 

 consider the rarer kinds of a blue or green colour. Green amber ranges in colour from a 

 pale to a blackish-green and from olive-green to the apple-green of chrysoprase, sometimes 

 exhibiting white clouds. The colour of blue amber may be azure-, sky-, or steel-blue. Both 

 blue and green amber is turbid, and, in fact, the turbidity has a close connection with the 

 colouring of the stone, for this is due not to the presence of pigment, but to a peculiar 

 modification of the rays of light caused by the presence of the numerous air-bubbles, which, 

 as we have seen above, is the cause also of the turbidity of amber. These minute air-bubbles? 

 to which both the colour and the turbidity of blue amber is due, are arranged in it in layers 

 of some thinness, just as in bastard or osseous amber ; and the colour phenomenon for which 

 they are responsible is of the same nature as that observed in other turbid media. When 

 subjected to the clarifying process blue amber loses both its turbidity and its colour, 

 assuming the yello\\- colour of ordinary amber. 



The phenomenon of Jluorescence is very conspicuous in some specimens of amber, these 

 appearing of a yellow to brown colour in transmitted light, but of a dark bluish or greenish 

 colour in reflected light. Fluorescent specimens of Prussian amber are rarely seen, but are 

 less uncommon among the amber-like resins of Sicily, Burma, and other localities. Not being 

 suitable for ornamental purposes they are scarcely ever worked, and are worth less than 

 specimens of ordinary amber. 



One serious drawback to the use of amber as an ornamental material is its tendency 

 to change in colour with the lapse of time. This change in colour is due to a chemical 

 alteration which takes place gradually from without inwards. Pale-coloured specimens 

 become darker, and those which were yellow become red or brownish-red. The change is 

 noticeable after the lapse of only a few years, but differs in character in different varieties 

 of amber. Clear amber becomes slightly darker and redder in colour and numerous cracks 

 develop in its substance. In bastard amber an external layer becomes brown in colour and 

 assumes a waxy lustre. Osseous amber acquires a porcelain-like lustre, and in frothy amber 

 an external layer, sharply marked off from the remainder, becomes quite clear but brittle. 



These alteration processes proceed gradually, especially along cracks in the material, 

 until the whole mass has undergone the change. They were at one time attributed to the 

 action of light, but have since been observed to take place in the dark. When a piece of 

 amber is kept in water or otherwise excluded from contact with air, the change which takes 

 place in it is much less in extent, so that the process is simply a case of atmospheric 

 weathering. 



Under natural conditions the weathering process has sometimes proceeded so far that 

 only a small nucleus of the mass remains fresh and unaltered, the outer shell being much 

 cracked and fissured, and its surface honeycombed M'ith a shallow sculpturing, such as is 



