12 



BULLETIN 149, UNITED STATES NATIONAL MUSEUM 



Berwerth has described ^^ under the name of " Netzbronzit " a 

 fibrous form of bronzite occupying the interstices of porphyritic 

 oU vines in the Zavid stone, the fibers standing at right angles to the 

 oUvine surfaces. These he considers due to a partial fusion and 

 recrystailization of the fine bronzite material in a chondritic tuff. 



2. Monoclinic p3^roxenes: Augite, diopside, and diallage. These 

 forms of pyroxene are, on the whole, less common in meteorites than 

 are the ortho rhombic forms, though it is possible that they are in 

 reality more abundant than is generally supposed, their close resem- 

 blance in all but optical properties (which, owing to the small size 

 and poorly developed crystallization, can not always readily be de- 

 termined) rendering a sure discrimination somewhat difficult. The 

 composition is, presumably, fully as variable as that of the enstatites, 

 but few actual analyses of pure materials have been made, owing to 

 the difficulty in separating them from the associated minerals. 

 Of the fofiowing analyses, No. I is by Maskelyne ^^ and II by 

 Tschermak.^^ 



Silica (SiOa) 



Alumina (AI2O3) 



Ferric oxide (FezOs)- 

 Ferrous oxide (FeO). 



Magnesia (MgO) 



Lime (CaO) 



Soda (NazO) 



Sp. Or. 



Constituents 



Source 



I Busti 



23.33 



19.98 



.55 



99.90 



II Sher- 

 gotty 



52.34 

 .25 



23.19 

 14.29 

 10.49 



100. 56 

 3.466 



As with other silicate constituents, the monoclinic pyroxenes are 

 but poorly developed crystallographically, with irregular and very 

 imperfect cleavage, and are nearl}^ colorless, though the diopside is 

 often of a bright green in tinge as in the iron of Four Corners, N. Mex. 

 (See pi. 9.) They are often intergrown with enstatites and are rarely 

 appreciably pleochroic. The so-called jpeckhamite of J. L. Smith is 

 but an altered bronzite.^" 



Radium. — See under gases, p. 6. 



Schreihersite (and Rhabdite) .—This mineral, first described and 

 named by Haidinger in 1847 as a constituent of the Magura iron and 

 since found one of the commonest of the accessory meteoric constit- 

 uents, is a phosphide of nickel iron and cobalt, corresponding ap- 

 proximately to the formula (FeNiCo)3P. It occurs commonly in thin^ 



" Wissenschafr. Mittheil. aus Bosnianu. der Hercegovina, vol. 7, 1901. 



28 Philosophical Transactions, vol. 160, 1870. 



2» Sitz. des k. Akad. des Wiss., vol. 65, 1872. 



so See Merrill, Proc. U. S. Nat. Mus., vol. 58, 1920, p. 634. 



