NO. 1524. ON THE RICH MOUNTAIN METEORITE— MERRILL. 243 



posed of a single mineral, the optical properties of which are so ill- 

 detined as to make a satisfactory determination impossible. At times 

 it is quite isotropic, but more commonly it shows a faint double 

 refraction, and in a very few instances the attempt at obtaining- an 

 interference figure resulted in a yery indistinct dark brush, suggestive 

 of a biaxial mineral. Between crossed nicols, if not always dark, it 

 shows no definite extinction plane, but the dark wave sweeps over the 

 surface much as in an isotropic mineral in a condition of strain. In a 

 .single instance one of these areas adjoined and partially inclosed a 

 minute particle showing the parallel twin bands of a plagioclase feld- 

 spar. The mineral is regarded as unquestional)ly the same as that so 

 common under similar conditions in the meteorite of Altianello, Italy, 

 and which has been considered b\^ V. Toullon'^' as maskehmite, a con- 

 clusion adopted b}' Tschermak.^ The present writer also noted its 

 occurrence in the recently described meteoric stone from Coon Butte, 

 Arizona,'' Compared with terrestrial rocks, it is of interest to note 

 that similar structures and associations of pyroxene or olivine, and 

 what are unquestionably feldspars, are found in peridotites of the 

 wherlite type, as described f' by the writer some years ago from the 

 Red Bluff region of Montana. 



In addition to the a])ove is an occasional plate of a colorless silicate 

 likewise of a doubtful nature. The plates are of irregular outline, 

 faintly gray or almost completely colorless, and show very faint, short, 

 sharp cleavage lines, and rarely any inclosures of other minerals which 

 are so conspicuous a feature of the maskelynite. The surface viewed 

 under a high power has a peculiar roughness, in which also it differs 

 from the above. Between crossed nicols it gives weak polarization 

 colors, and is optically biaxial, though good interference figures are 

 not o})tainable. The description given by Tschermak'' of a mineral 

 referred to as possibl}" monticellite would apply equally well to this, 

 though the present writer confesses to a considerable feeling of doubt 

 as to its true nature. 



The structure and composition of the stone, as a whole, is compar- 

 able with those of Lancon, France, and Bath Furnace, Kentucky (Cia). 

 It will be known as the Rich Mountain meteorite, 



CHEMICAL ANALYSIS BY MR. WIRT TASSIN. 



A ver}' small portion of the meteorite, 5.8 grams in all, was available 

 for analysis. This was treated in the usual way, the native metals 

 (I), sulphur (II), phosphorus (III), soluble and insoluble silicates (IV 



«Sitz. Wien. Akad., LXXXVIII, 1883, p. 433. 



&Die Mikroskopische Beschaffenheit der Meteoriter, see especially pi. xvii, fig. 2. 



cAm. Jour. Sci., XXI, May, 1906, p. 347. 



dVxoc. U. S. Nat. Mus., XVII, 1895, p. 651. 



f Sitz. Wien. Akad., LXXXVIII, Pt. 1, 1883, p. 355. 



