THE LINWOOD METEORITE — HENDERSON AND PERRY 359 



The composition of the metallic portion of the Linwood meteorite 

 agrees very closely with that of the El Burro/ although in the latter 

 the kamacite bands are very broad (2-3 cm.) and fairly regular in 

 direction. The structure of the Murnpeowie ^ is entirely different, 

 consisting of rounded grains, small to moderate in size, without rec- 

 ognizable octahedral structure. 



Qualitative chemical tests were made upon the inclusions in order 

 to determine their nature. Graphitic carbon is present in all the sili- 

 cate inclusions; troilite was positively identified by collecting the 

 hydrogen sulphide gas liberated when the powder was treated with 

 hydrochloric acid; schreibersite was recognized by its physical habit 

 and its strong magnetic properties. The acid extract from the sili- 

 cates was found to contain magnesium, calcium, iron, nickel, traces of 

 phosphorus, and soluble silica. 



The bulk of the silicates is olivine, but there may be a small quantity 

 of anorthite present since the quantity of calcium found in the acid sol- 

 uble extract appears too large to be calcium derived from impurities 

 in olivine. The silicates insoluble in hydrochloric acid were washed 

 with dilute sodium-carbonate solution to remove the silica which had 

 separated by acid attack on the olivine, and then air-dried for optical 

 examination. Because of the complex nature of these silicates and 

 the difficulty of obtaining enough material to make mineral separa- 

 tions and chemical analysis, the authors decided that an optical study 

 would give results capable of more accurate interpretation. 



The general character of the olivine was determined by assuming 

 that all the magnesium found in the acid soluble portion was derived 

 from olivine, combining it with the total of the acid-soluble silica and 

 then adding enough FeO to give the theoretical olivine ratios. 



COMPOSITION OF OLIVINE FROM LINWOOD, NEBRASKA, METEORITE 



3 



SiO. 0.0468 grams 0.1470 1 



MgO 0.0707 grams 0.1753 



'FeO 0.1187 grams 0.1187 



^ Calculated. 



The partial analysis given above indicates an olivine with a com- 

 position midway between the magnesium and iron ends of the series 

 very close to Fo6oFa4o. 



Optical properties of the silicates in the acid-insoluble residue of 

 the Linwood, Nebraska, meteorite were determined by Miss Jewell J. 

 Glass, of the U. S. Geological Survey, and Dr. Harry H. Hess, of 

 Princeton University, to whom grateful acknowledgment is made. 

 The following data are quoted from their reports : 



"Most of the insoluble residue consists of graphite. 



1 Henderson. E. P., Amer. Min.. vol. 26. pp. 655-656. 1941. 



2 Spencer, L. J., Min. Mag., vol. 24, No. 148, pp. 13-20, 1935. 



