1888.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 119 



\yiug with their longer axes parallel, whieh give extinctions nearly, if 

 not quite, parallel with those axes. Except so far as to show the homo- 

 geneity of the mineral, the optical examination is quite unsatisfactory. 



The New Zealand jade, as seen under the microscope, consists wholly 

 of a very compact aggregate or felt-like mass of confused scales and 

 minute fibers, arranged in bundles and tnfts in a maimer which can be 

 best understood by a reference to fig. 1. The dark interstitial portions 

 there shown are, when the stage is revolved and the nicols are crossed, 

 seen to be composed of fibers and tufts of the same character as the 

 lighter parts. In ordinary light these are almost perfectly colorless, 

 and not perceptibly pleochroic. Between crossed nicols they show bril. 

 liant polarization in yellow, red, and purple colors. The fibrous, bent 

 and tufted form of the mineral renders a determination of its optical 

 properties difficult, and in many cases impossible. In the few instances 

 i hat they are gathered into long bundles in which the fibers are lain 

 approximately parallel, they are found to give extinction angles varying 

 from 0° to 20°, indicative of a mineral of the amphibole group — an indica- 

 tion fully borne out by the analysis. The only inclosuresare minute, dust- 

 like particles of a black or yellow color, evidently ferruginous, but which 

 a power as high as 750 diameters fails to satisfactorily determine. This 

 structure is identical with that shown by slides in the museum collec- 

 tion made from jade implements from New Zealand. Jade from the same 

 locality has also been studied by Arzruni,* who describes it as an ex- 

 traordinarily dense mass of bent and contorted fibers, stained yellow- 

 ish in spots by iron oxide, and without iuclosures. Our analysis agrees 

 sufficiently well with that of Mr. C. L. Alient of a jade from the same 

 locality, to insure identity of material. 



The same structure, with slight modifications, is common to the 

 nephrites of New Caledonia and Siberia, as shown by sections of them 

 iu the Museum collection. Indeed, this finely fibrous and tufted struct- 

 ure appears to be characteristic of true nephrite, from whatever locality. 

 Thus, Arzruni! describes a nephrite from southeastern Alaska as pos- 

 sessing a microscopic structure uniformly fine and fibrous throughout. 

 The fibers, though but little bent and curved, seldom lie parallel with 

 one auother, but are gro uped into loose, irregularly-outlined, and tufted 

 bunches. In the less compact portions the fibers intersect each other 

 at approximately right angles, forming a grate-like, reticulated struct- 

 ure. This he regards as a commencement of alteration into what may 

 be serpentine or bastite. Such an alteration is accompanied by a slight 

 browning of color, due to the liberation of iron oxide. He regards the 

 isolated fibers as a variety of amphibole, and compares the general 

 structure with that of a nephrite from the Kitoj River, Irkutsk, Siberia, 

 which has been described by Beck and Muschketow, and which will be 

 noted later. He states, however, that it differs from the Siberian 



* Zeit. fur. Ethnologic, 1883, p. 183. 



t Chera. News, 1882, p. 216. 



\ Jahresbericlit des Vereiua f. Erdkunde zu Dresden, 1885, p. 6. 



