no. 2084. THE FISHER, POLK COUNTY, METEORITE— MERRILL. 505 



of the surface once continuous over the entire mass (A in plate). 

 The remaining surfaces, which are plainly due to the fracturing of 

 the stone in the lower atmosphere, are characterized by shallow 

 pits. All are coated with a black, lustreless, somewhat rough coating 

 caused by the unequal fusibility of the various constituents. This 

 is plainly shown in the half tone reproductions from the photographs. 

 Three crusts are recognizable (1) that first formed (A in plate), (2) 

 a thinner crust covering the earliest fractures, and (3) a very thin 

 crust covering limited areas of secondary fracture. I find no certain 

 evidence of a quarternary coating, as mentioned by Doctor Hovey, 

 on the specimen in the American Museum. 



Under the microscope the stone is found to consist of a confused 

 aggregate of irregular crystalline granules of olivine and pyroxene 

 interspersed with numerous imperfectly outlined chondrules, con- 

 sisting also of olivine and pyroxene, throughout which are occa- 

 sional interstitial areas occupied by a colorless, pellucid, faintly 

 doubly refracting or quite isotropic material, referred to maskelynite. 

 Small areas of nickel and iron sulphide complete the list of deter- 

 minable minerals. The chondrules are sometimes wholly of pyroxene, 

 either in stout irregular crystals or in fan-shaped and dendritic 

 forms, and sometimes of olivine, the latter also in barred and radiating 

 forms. Both types of chondrules contain numerous inclosures of 

 the colorless mineral mentioned above. No truly porphyritic forms 

 were noted. The pyroxenes all give parallel extinctions and are 

 devoid of twin structure. The colorless interstitial material seems 

 sometimes quite isotropic or again faintly doubly refracting, with 

 an index of a refraction of but 1.51 as determined by the immersion 

 method. 1 



A chemical analysis on materials selected to insure its representa- 

 tive character, yielded Dr. J. E. Whitfield results as below: 



Per cent. 



Metallic constituents 11. 44 



Silicate constituents 88. 56 



The silicate portion yielded: 



Per cent. 



Silica, Si0 2 43. 70 



Alumina, A1 2 3 4. 96 



Ferrous oxide, FeO 18. 27 



Manganous oxide, MnO 0. 38 



Nickel oxide, NiO 0. 23 



Lime, CaO 2. 19 



Magnesia, MgO 29. 38 



Chromite, FeO.Cr 2 3 0. 80 



99.91 



1 It should be noted in this connection that Professor Winchell, in the description above referred to, 

 noted the mineral composition essentially as I have given it. 



