THE CONSTITUENTS OF METEORITES 397 



Chrysolite. — This is, next to nickel-iron, the chief mineral 

 constituent of meteorites. It is found in all the iron-stone and 

 nearly all the stone meteorites and makes up a large part of 

 their mass. It occurs as crystals and as rounded and angular 

 grains. In the group of iron-stone meteorites known as palla- 

 sites it is porphyritically developed in the nickel-iron; in other 

 iron-stone meteorites it forms together with pyroxene a granular 

 aggregate filling the meshes of a network of nickel-iron. In the 

 chondritic meteorites the manner of its occurrence has already 

 been described. Crystals occurring in cavities or isolated by 

 dissolving adjacent nickel-iron lend themselves readily to gonio- 

 metric measurement. A total of twenty forms, similar to those 

 found on terrestrial chrysolite has thus been identified. The 

 color of the mineral is usually the typical olive-green of terres- 

 trial chrysolite but may vary to honey-yellow or red. Much of 

 the meteoritic chrysolite is characterized by an abundance of 

 opaque inclusions often regularly arranged. Intergrowths with 

 a colorless to dark brown glass are also common, especially in 

 the chrysolite of chondritic meteorites. Gas pores are rare- 

 Alteration products so common to terrestrial chrysolite are 

 entirely lacking. Much of the chrysolite shows a strong ten- 

 dency to fissuring, especially in thin sections. Well-marked 

 cleavage is not common. Numerous analyses of mechanically 

 separated chrysolite show a composition similar to that of the 

 terrestrial mineral. The percentage of Fe in these analyses shows 

 variations from about lo per cent, to about 30 per cent. One 

 feature of the composition of meteoric chrysolite which seems 

 at first difficult to account for, is an almost entire lack of nickel 

 oxide. This, as is well known, is a very constant constituent of 

 terrestrial chrysolite. Daubree has shown, however, that an 

 absence of nickel from meteoritic chrysolite should be expected, 

 since nickel has less affinit}' for oxygen than iron and would not 

 be attacked until the latter was completely oxidized. While ter- 

 restrial iron has been completely oxidized that of meteorites has 

 not. The correctness of this explanation has further been shown 

 experimentally by fusing terrestrial chrysolite with pyroxene in 



