COMPOSITION AND STRUCTURE OF METEORITES 21 



Four Corners meteorite. This is described ^^ as "a granular mass 

 of octahedral iron with silicate inclosures" which in this case are 

 mainly pyroxenic. It is to be noted that each granule of the metal 

 has its own crystallographic orientation, the structure as a whole 

 resembling very much that of a coarsely crystalline aggregate of 

 calcite or feldspar. The pyroxenic portions (dark in the figure) are 

 finely granular and sometimes in the condition of a fine sand. The 

 closest analogue to this peculiar iron is thought to be that of Copiapo 

 (Dheesa), Chile, as described by various authorities. 



A second type which might well be mentioned here is that of Per- 

 simmon Creek in Cherokee County, N. C. (Lower figure, pi. 9.) This 

 peculiar mass is described** as "a granular octahedrite" but might 

 better be designated as an agglomerate of masses of metal and troilite 

 (A and B in the plate), and occasional dark masses consisting of a 

 dense aggregate of graphite, troilite and olivine (C in the plate). 

 The metallic portions are composed of granules each with its own 

 crystallographic orientation and an octahedral structure as in the iron 

 of Four Corners. 



2. STONY-IRON METEORITES: SIDEROLITES 



The stony-iron meteorites are classified as (1) Lodranites, crystalline 

 granular aggregates of olivine and bronzite in a fine network of metal. 

 But one of this type is known — that of Lodran, India, which fell in 

 1868 and of which but 970 grams are known to exist. (2) Mesosider- 

 ites, or grahamites, aggregates of olivine, bronzite, plagioclase, and 

 augite, sometimes chondritic or with a crystalline structure in a con- 

 tinuous net of metal. (3) Siderojjhyres consisting of bronzite and 

 nickel-iron with accessory asmanite (tridymite). But a single meteor- 

 ite of this type also is known- — that of Steinbach (Breitenbach) Sax- 

 ony, which was not seen to fall but was found in 1751. (4) PaUasites 

 consisting of olivine in a continuous network or sponge of metal. 

 With the stony irons are also included by some authorities breccia- 

 like masses of nickel-iron with crystalline chondrites like that of 

 Copiapo and the octahedral iron with crystalline chondrites of 

 Netschaevo. 



Meteorites of the mesosiderite or grahamite group are well rep- 

 resented by the finds of Crab Orchard (Rockwood), Morristown, 

 Hainholz, and Vaca Muerta. The fall of Estherville though com- 

 monly here classed is really of a somewhat different type. The com- 

 mon structure, as shown in Plate 12, is that of a dense net or sponge of 

 metai the interstices of which are filled by silicate minerals in the form 

 of small, single and angular particles and aggregates it may be two or 

 more centimeters in diameter. The metal is rarely segregated in 

 blebs a centimeter in diameter which yield Widmanstatten figures 



« Proc. Nat. Acad, of Sciences, vol. 10, 1924, p. 312. 

 " Proc. U. S. Nat. Mus., vol. 27, 1904, p. 955. 



