55a SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



is exported in large quantity from East and West Africa, South America, and Australia. 

 In colour and general appearance it resembles some kinds of amber, and, like this substance, 

 often encloses insects, but articles made of copal always have a dirty appearance. Owing to 

 its lower melting-point copal, when rubbed with the hand or on cloth, becomes sticky ; it is 

 soft enough to take an impression even of the finger-nail, and when immersed in acetic ether 

 it loses its lustre and swells up. All these characters serve to distinguish it from amber, 

 and, if more were needed, it becomes less strongly electrified on rubbing, and, when burnt, 

 does not give oft' the smell characteristic of amber. In order to produce the latter 

 feature copal is sometimes melted up with pieces of amber, but owing to the difference 

 in the melting-points of the two substances they do not mix, and after the mass has 

 solidified the pieces of amber are easily recognisable lying in the copal. This substance is 

 unsuitable for certain of the uses to which amber is put ; for example, it is too brittle to 

 allow of the worm of a screw being cut on it. 



Dammar-resin mixed with powdered amber, and clear copal-colophony mixed with 

 Venetian turpentine, furnish materials for the manufacture of imitation amber articles, such 

 as cigar-holders. These imitations of amber show a turbid, " kumst "-coloured ground-mass, 

 in which lie sharply defined masses of clear material, and in which insects— often ants— are 

 embedded. The artificiality of this substance is very apparent, for clear and bastard material 

 is rarely seen in combination in genuine amber, and, moreover, when the mass is broken it 

 become? obvious that the insects are made of metal. If made of copal the substance 

 quickly swells up when placed in acetic ether, and if it consists of dammar-resin it loses its 

 lustre when immersed in sulphuric ether for a period of from ten to fifteen minutes. Genuine 

 amber is only affected after a much longer subjection to this treatment. Like copal 

 damraar-resin also becomes sticky \\hen rubbed. 



Amber containing enclosures is sometimes manufactured by boring a hole into a suitable 

 j)iece of genuine amber, placing some animal, such as a lizard or a tree-frog, in the hole, 

 and filling it up with melted dammar-resin. It is not uncommon to find objects so 

 treated mounted in gold and highly prized by the unsuspecting owner. When treated 

 with alcohol or ether the melted resin is, of course, easily dissolved out. 



The use of the imitations of amber described above is now almost superseded by 

 that of pressed am.ber or ambroid, a substance produced from genuine amber, and 

 first brought into the market at Vienna. Attempts had been made from time to time to 

 devise some means of utilising small pieces of amber other than by converting them into 

 varnish. This was at last accomplished, and the smaller pieces of amber are now welded 

 together, as it were, by the application of a great pressure and an elevated temperature. 



The method employed depends upon the fact that at a temperature between 170° 

 and 200° C. amber softens. Pieces of rough amber after being freed from all impurities are 

 placed in a flat mould of steel, the steel cover of which is then hermetically sealed. The 

 mould is then placed in an oven, of which the temperature can be regulated to a nicety, or 

 in a bath of glycerine or paraffin. By means of the hydraulic press, a pressm-e of from 

 8000 to 10,000 atmospheres is applied to the cover of the mould, and this pressure welds 

 the pieces of amber, which are softened by heat, together to form a flat cake. These 

 flat cakes of pressed amber are known in the trade as Spiller imitations. A much finer 

 product is obtained when the amber, softened by heat, is driven under high pressure through 

 a metal sieve, the resulting mass being by this method more thoroughly intermixed. 



The pressed amber so produced can be obtained in all the varieties in which amber 

 occurs, the " flohmig " and clear material being remarkably similar to natural amber. 

 There is a difference apparent under the microscope however, for the rounded cavities of 



