THE SPANG COLLECTION OF MINERALS. 447 



color is a translucent green — in most other recorded cases it is yellow 

 or brown. 



One of the most curious specimens is a natural amalgam of silver. 

 It is a dodecahedral crystal, one-half an inch by three-eighths in size, 

 which communicates, by a solid rod of the same material passing 

 through the interior of the rock and nearly concealed from view, with 

 a similar crystal of amalgam. When placed in such a position that 

 one crystal is vertically above its mate, and allowed to stand for a 

 short time, the mercury finds its way downward and distends the 

 lower crystal until its faces are quite obliterated. In fact, it is con- 

 verted into a pear-shaped drop, and looks as if it were about to fall 

 from the crystal. When the specimen is inverted and allowed to re- 

 main so for half an hour, the mercury percolates through the solid 

 mass of amalgam, the distended crystal acquiring its former definite 

 outlines, and settles into a drop depending from the apex of crystal 

 No. 1. This lusus naturce, an hour-glass of metallic crystals, is, I be- 

 lieve, without parallel. 



Then there is a resplendent crystal of axinite from Switzerland, 

 among multitudes of others, which is three inches upon one of the 

 faces and four inches measured along its greatest dimension ; and a 

 cluster of stibnite crystals from Hungary, weighing perhaps five 

 pounds, of which the largest crystal is a prism three inches long and 

 three-eighths of an inch thick, perfectly terminated. 



In conclusion, the emeralds deserve our admiration, as they 

 would that of persons least sensible of natural beauty. Of these, 

 there is a number of large crystals, some mounted upon the rock in 

 which they occur, others detached. Some of the latter from Bogota 

 have highly-modified terminations. Although not so large as the 

 others, being but one-half an inch in length and three-eighths of an 

 inch in thickness, by far the finest emerald is one which is implanted, 

 along with smaller crystals, upon a piece of rock from the Ural Moun- 

 tains. It has a perfect termination, presenting very many rhombohe- 

 dral and pyramidal planes. Without a flaw, absolutely limpid, and of 

 wonderful purity and depth of color, it is a natural gem, in the eyes 

 of a mineralogist incomparably more beautiful than any cut and 

 polished jewel could be. Its history might suggest to the writer of 

 fictions some features of a romance, it having been given by a Czar 

 of Russia to Taglioni, and subsequently placed by her in pawn with a 

 wealthy gentleman in Paris. 



