121 



NEPURITE AND JADE1TE. 



black specimen. L00516, were examined further, and an analysis was 

 also made of n fragment of massive saussurite from the Saas Valley, 

 Switzerland, oul of the Museum collection. The results of analysis 

 were as follows : 



[pnition • 



Silica 



Alumina 



I en ic oxide , 



Ferrous oxide 



Manganous oxide. 



Lime 



Magnesia 



Soda 



Potassa 



Fibrolite, 



1.31 

 34.66 

 63.24 

 trace 



From 



Bstavayer, 



100516. 



none- 

 .37 



99.58 



. 65 

 4."). 13 

 16.55 

 13.59 



4. 20 

 i pace 

 11.02 



5. 18 

 3. 89 



t race 



Saussurite, 



100586a. 



.30 

 49. 90 

 29. 76 



Saussurite, 

 massive. 



100. 51 



11.77 

 5. 80 

 3.21 



trace 



.54 

 18.29 



27. 05 



1.45 



12.95 

 5. 30 

 3.57 



trace 



100. 2G 



99. 81 



Chemically the second of these rocks is like a saussurite, saussurite 

 itself being a very variable mixture, ranging from mainly a zoisite to 

 mainly a feldspar. Microscopically, however, it is seen to be a mixture 

 of various minerals, and is evidently a highly altered basic rock, possi- 

 bly a diorite. Jf so, the original constituents are now so completely 

 altered as to be scarcely recognizable. The most abundant constituent 

 is a bright green or bluish amphibolic mineral, mixed with more or less 

 chloritic matter and various decomposition products. Throughout this 

 ground-mass are scattered abundant yellowish grains and granular 

 aggregates of secondary epidote, a colorless mineral with the optical 

 properties of zoisite, and rounded grains of an iron ore, each inclosed 

 in a narrow, nearly colorless border of leucoxene (?). The felspars, if 

 such existed, are no longer recognizable. Other minerals of a second- 

 ary nature are present, but need not be alluded to here. 



As for the fibrolite, No. 100238, this is shown by the microscope to be 

 made up of innumerable minute, greatly elongated, colorless needles 

 arranged in bundles with their longer axes approximately parallel, often 

 broken transversely, and crowded into a dense mass, and usually with 

 a decided plumose structure. The needles are to minute for a deter- 

 mination of their optical properties. These needles make up the entire 

 mass of the rock, except for a few minute rounded granules, which are 

 quite opaque and resemble an iron ore. 



The question has been asked if there are any means by which an ob- 

 ject may be identified as nephrite or jadeite without resorting to the 

 destructive process of cutting a thin section or making other tests such 

 as will involve a more or less defacement of the object. In a general way 

 it may be stated that thejadeites are of a distinctly granular, or at least 

 scaly-fibrous texture, while the nephrites are uniformly fibrous and 

 compact throughout, These distinctions can sometimes be detected by 



