310 



SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



1350 carats; it is of the finest colour, clear and transparent, and almost faultless. This 

 stone came from the emerald mines at Muzo in Colombia, where crystals of the length and 

 thickness of a finger are by no means rare. Crystals of equal size are found in the Urals 

 and are not specially rare ; one measuring 8 inches in length and 5 inches in diameter 

 is preserved in the collection of the Imperial Institute of Mines in St. Petersburg, and still 

 larger crystals have been reported. Probably the largest is in the possession of the Czar of 

 Russia ; it is said to measure 25 centimetres "(nearly 10 inches) in length and 12 centimetres 

 in diameter. One or two very large stones, formerly thought to be emeralds, have on closer 

 examination proved to be green glass ; such, for example, is one weighing 28f pounds in the 



Reichenau monastery above Chur, in the Rhine 

 Valley, Switzerland. 



The form in which an emerald is cut depends 

 upon the character of the rough stone. Perfectly 

 faultless, transparent fragments, when not too 

 dark, are cut as brilliants or as rosettes. Most 

 frequently, however, the step-cut (Plate XII., 

 Fig. 3) with brilliant facets on the upper portion 

 is adopted. The emerald, though not infre- 

 quently cut as a simple table-stone, is probably 

 never, at least in Europe, cut en cabochon. Cut 

 gems, pei-fect in colour and transparency, are 

 mounted a jour ; paler stones are provided with 

 a green foil placed beneath them, while fissured 

 or otherwise faulty stones are mounted in a 

 closed setting blackened inside. 



Natural crystals of emerald are, as a rule, 

 too large and too much flawed to be cut as 

 single gems ; they are, therefore, sawn into por- 

 tions of suitable size and purity, great care being 

 taken to avoid unnecessary loss of material. In 

 many crystals, clear and transparent portions 

 suitable for gems have to be cut out of the main mass of the crystal, and in this operation 

 special care is required. Each portion so cut out of a crystal is faceted in the form best 

 suited to its particular shape. 



Compared with the precious stones hitherto considered, the emerald, in its mode of 

 occurrence, is unique, for it is found exclusively in its primary situation, that is to say, in 

 the rock in which it was formed. It is one of the minerals characteristic of crystalline 

 schists, and in many places is found embedded in mica-schists and similar rocks. The 

 famous occurrence at Muzo in Colombia is the only exception to this rule, the emerald 

 being here embedded in calcite veins in limestone. This occurrence has called forth the 

 perfectly groundless supposition that the emeralds here were originally formed in crystalline 

 schists and were afterwards deposited in the calcite veins. The emerald practically never 

 occurs in gem-gi'avels, in the way in which diamonds, rubies, &c., occur. 



The earliest known emerald locality is doubtless that in Upper Egypt, not far from 

 the coast of the Red Sea and south of Kosseir. Though the occurrence of emerald in 

 Ethiopia was known to the ancients, the locality, in course of time, became completely 

 forgotten, and ancient accounts of the occurrence were regarded as erroneous. It has been 

 supposed that true emeralds were first introduced into Europe at the end of the sixteenth 



Fig. 63. Crystal of emerald belonging to the 

 Duke of Devonshire. (Actual size.) 



