NOTES ON THE COMPOSITION AND STRUCTURE OF THE 

 INDARCH, RUSSIA, METEORIC STONE. 



By George P. Merrill, 

 Head Curator, Department of Geology, United States National Museum. 



This interesting stone fell, according to V. Siemaschko, on April 7, 

 1891, though Meunier * gave the date as April 9. According to 

 Wiilfing's catalogue the stone has since been described by Tarassow, 

 but seems never to have been subjected to a thorough microscopic or 

 chemical investigation. I have, therefore, included it in the studies 

 on the minor constituents on which I have been engaged. ^ 



It is stated by Meunier that in falling the stone buried itself in the 

 soil to a depth of 18 cm. and scorched the vegetation for a radius of 

 10 meters, being stiU hot when exhumed 10 hours later. The dark 

 color he regarded as due to the heat to which it had been subjected, 

 and he claimed to have produced similar results in the laboratory 

 on stones of his Montrejeit groilp. 



Macroscopically the stone is of a dark greenish gray color, firm and 

 compact, admitting of a polish, and on the polished surface thickly 

 studded with smaU, dark, almost black chondrules and nodular 

 masses of metal and troUite, the largest of which are rarely over 1 

 mm. in diameter. Under a pocket lens the chondrules are mostly 

 of a green color, though some are nearly black. They break with the 

 matrix in which they are embedded. In thin sections and under the 

 microscope the structure is quite obscure owing to the prevalence of 

 graphite, which everywhere impregnates it. It presents a dense 

 black irresolvable ground throughout which are scattered the iron 

 and iron sulpliide, together with abundant sharp splinters of pyi'oxene 

 and numerous more or less fragmentary chondrules of the same 

 mineral in both porphyritic and radiating forms (see pi. 37). All 

 of the well crystalhzed forms, both in isolated particles and in the 

 chondrules, belong to the polysyntheticaUy twinned cUno-enstatite 

 type. No olivine, feldspar, or other siUcate mineral was determined, 

 though carefully sought, as their presence was suggested by the 



• Comptes Rendus, vol. 125, 1897, p. 894. 



2 See preliminary paper, Amer. Joum. Sci., vol. 35, 1913, pp. 509-525. 



Proceedings U. S. National Museum, Vol. 49— No. 2098. 



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