AMBER, a fossil resin much used for the manufacture of ornamental objects. The name comes from the Arabian anbar, probably through the Spanish, but this word originally referred to ambergris, which is an animal substance quite distinct from yellow amber. The property which amber possesses of acquiring elec trical charge by friction is first recorded by Thales of Miletus, and suggested the word "electricity" from the Greek, iiXei rpov, a name applied, however, not only to amber but also to an alloy of gold and silver.
Amber is not homogeneous in composition, but consists of sev eral resinous bodies more or less soluble in alcohol, ether and chloroform, associated with an insoluble bituminous substance. The average composition of amber leads to the general formula In concentrated sulphuric acid finely powdered amber is perfectly soluble even in the cold, and it is completely decomposed by boiling nitric acid. Heated rather below 3oo°C. amber suffers decomposition, yielding an "oil of amber" and leaving a black resi due which is known as "amber colophony," or "amber pitch"; this forms, when dissolved in oil of turpentine or in linseed oil, "amber varnish" or "amber lac." True amber yields on dry distil lation succinic acid, the proportion varying from about 3. to 8% and being greatest in the pale opaque or "bony" varieties. The aromatic and irritating fumes emitted by burning amber are mainly due to this acid. True Baltic amber is distinguished by its yield of succinic acid, for many of the other fossil resins which are often termed amber contain either none of it,-or only a very small proportion ; hence the name "succinite" proposed by Prof. J. D. Dana, and now commonly used in scientific writings as a specific term for the real Prussian amber.
The physical characters of amber are in every respect those of a resin. It is perfectly amorphous, as is shown by the recent X-ray investigations of Prof. F. Rinne. It occurs in irregular rounded nodules having the form of rods, drops, plates, etc., and never in masses bounded by plane surfaces. The specific gravity of amber ranges from I •os to 1•10; the substance is thus only slightly heavier than water. Its hardness, H = 21, is a little greater than that of gypsum, and it is therefore just not possible to scratch it with the finger-nail. It is harder than most other resins but is not very brittle and can therefore be carved, worked on the lathe or bored with little difficulty. When rubbed on cloth amber becomes strongly charged with negative electricity, and attracts small light particles. It is also a very good insulator for use in electrical ap paratus and is superior to sulphur because of its mechanical prop erties. The colouring of amber is very uniform in character, no colour but yellow occurring in the great majority of specimens, though all shades of this colour, from the palest yellow to brown, are known, The turbidity of certain kinds of amber is due to the inclusion of great numbers of minute air bubbles. Various other enclosures are found in amber, some of which are of special significance. Drops of water sometimes occur, but enclosures of solid matter, either organic or inorganic, are more frequent. The enclosures of organic material, partly of vegetable and partly of animal origin are of great importance, as they have thrown much light on the flora and fauna existing at the time of the exudation of the amber.
Amber is extensively used for beads and other small ornaments, and for cigarette-holders and the mouth-pieces of pipes. Small fragments, formerly thrown away or used only for varnish are now utilized on a large scale in the formation of "ambroid" or "pressed amber." The pieces are carefully heated with exclusion of air and then compressed into a uniform mass by intense hy draulic pressure. Rods of amber are then obtained by forcing the mass of softened amber through holes in a metal plate. The prod uct possesses practically the same physical properties as natural amber.
The greatest amber-producing region is the promontory of Samland in East Prussia, where the amber occurs in a marine glauconitic sand, known as "blue earth," occurring in the Lower Oligocene strata. It appears, however, to have been partly derived from yet earlier Tertiary deposits (Eocene) and it occurs also as a derivative mineral in later formations, such as the drift. Rolled pieces of amber may be picked up at various places along the east coast of England and also on the coasts of Holland, Denmark, Sweden, in Bornholm and other islands and in South Finland. Varieties of amber differing slightly from succinite are found in Rumania, Sicily and Burma.
BIBLIOGRAPHY.-H. Conwentz, Monographie der baltischen BernBibliography.-H. Conwentz, Monographie der baltischen Bern- steinbaume (1890) ; R. Klebs, Guide to Exhibit of the German Amber Industry at World's Fair (St. Louis, 1904) ; G. F. Kunz in Mineral Resources of the U.S. (1904) ; Max Bauer, Precious Stones, Eng. trans. by L. J. Spencer (19o4) ; F. Kaunhowen, "Der Bernstein in Ostpreussen" (Jahrb. d. Konigl. Preuss. Geol. Landesanstalt fur 1913). For Burmese amber, papers by Fritz Noetling and Otto Helm in Records of Geol. Surv. of India, vol. xxvi. (1893) ; for British amber, Clement Reid in Trans. Norfolk Nat. Soc., vols. iii. (1884) and iv. (1886) . (W. A. W.)