100 Scientific Proceedings, Royal Dublin Society. 



recognised. The mine was situated on the border of Negroland, 

 in Egyptian territory. The matrix of the gem was talc and red 

 earth. It seems probable that this was the source of the emeralds 

 which went to India, and also supplied the Greeks and Romans. 

 A soap-green emerald was also found at Hedshas, in Arabia. 



Owing to the fact that jade was not recognised as a distinct 

 mineral until introduced into Europe from the New World, the 

 older writers sometimes, on account of its hardness and transpa- 

 rency, spoke of it as emerald, while others applied to it the term 

 jasper. There can be no doubt that jade is meant by the follow- 

 ing, not jasper, as his translator has it : — 



Jaschep, or Nussz. — Five kinds: (1) white and light; (2) 

 whitish yellow ; (3) black-green ; (4) transparent black ; (5) dust- 

 colour. 



Mahomed adds that in China they make false jaschep, which 

 is distinguished by its smoky smell, and that there are two 

 mines in China called respectively Ak-Kash which produces light, 

 and Kut-Kash which produces dark jaschep. It is found on the 

 frontiers of Kashgar, Kerman, and Arabia. 



Kash is the name for jade current in Eastern Turkistan, and 

 su or zu is the name by which it is known to the Chinese, who 

 esteem it more highly than do the people of any other nation.^ 



Chrysolite? (Sheberdshed) . — This is said by Mahomed to be 

 obtained in the same mine as the emerald, of which it is a variety 

 according to some authorities. If so, it cannot be what is now 

 known as chrysolite, which is the transparent variety of olivine. 



Mahomed mentions a number of other minerals, among them 

 several ores. Of the magnet he says there are four kinds, namely, 

 the iron, gold, silver, and tin, which attract these metals respec- 

 tively ; possibly by this it is meant to be conveyed that ores ascer- 

 tained to contain these metals exhibited magnetic properties. 



The following statements, regarding the knowledge possessed 

 by the Persians of the relative specific gravities of some precious 

 stones, are of interest : — 



"Abu Rihan is said to have found by experiment that a 

 muskal ( = 1^ drachms) of blue yakut (sapphire) is equal to five 

 dank and a tissu of red yakut (ruby), or to five dank and two and 



1 Economic Geology, p. 516, et. seq. ; and also p. 109 of this Paper. 



