COMPOSITION AND STRUCTURE OF METEORITES 25 



secondary magnetite, pyrrhotite, and quartz in minor quantities. 

 The pyroxene of the unaltered fragments is of a brownish color and 

 filled with inclosures; that of the fine granular recrystallized ground 

 is of a yellowish color and free of inclosures. The howardites, of 

 which that of Teilleul is considered typical, is described as consti- 

 tuted almost exclusively of angular fragments of bronzite with fer- 

 ruginous inclusions; a " diopside-bronzite prive d'inclusions ferrugi- 

 nous" and anorthite, with some chromite. The group would seem 

 really to consist of the same materials as the cataclastic, pulverulent 

 interstitial portions of the eukrites. 



The stone of Juvinas consisting of a colorless anorthite and gray to 

 brownish augite shows under the microscope a holocrystalline struc- 

 ture not unlike that of many basic terrestrial rocks and like them 

 containing minute geode-like cavities. That of Shergotty (fig. 2, 

 pi. 16) difters in showing broad plates of brown augite with inter- 

 spaces occupied by a clear, colorless, and transparent feldspathic 

 mineral which is optically quite isotropic and to which the name 

 maskelynite has been applied. Stones of the Nakhla type (fig. 1, 

 pi. 16), of which but one example is known, consist of an even, granular 

 aggregate of green pj^roxene (diopside) with olivine and occasionally 

 a plagioclase feldspar and a little magnetite. It might well pass for 

 a terrestrial pj^roxenite. The chassignites, as represented by the 

 single occurrence in Chassigny, are fine crystalline granular aggregates 

 of olivine not greatly dissimilar to some terrestrial dunites. The 

 chladnites as represented by the Bishopville stone consist of a rather 

 coarse crystalline granular aggregate of nearly white enstatite with 

 small amounts of a plagioclase feldspar and occasional troilite granules. 

 The stone is remarkable for its poverty in metal, analyses showing less 

 than 1 per cent of this constituent.^^ 



In many meteorites (both chondritic and otherwise) a brecciated 

 structure is plainly evident even to the unaided eye. This may be 

 due to a commingling of rock fragments from diverse sources, or from 

 crushing in mass, or perhaps from both, as shown in the meteoric 

 stone which fell in Kentucky in 1919 (pi. 17). Here are plainly 

 commingled two types of stone which have been compressed suffi- 

 ciently to produce incipient twinning in the enstatite particles after 

 a manner well known to petrologists. The manner in which the 

 metal is disseminated throughout this stone is of interest and will be 

 referred to later. 



Other stones, like those of Supuhee, India, or Rose City, Mich., 

 are plainly agglomerates of pebble-hke bodies embedded in finer 

 material of the same mineral nature. In the St. Michel, Finland, 



« It is well to remark here that metal in the stony meteorites is present in appreciable quantities only in, 

 those the fragmental and tuffaeeous origin of which is readily apparent and is almost completely absent 

 in the crystalline or achondritic varieties. 



