1913-] EXCHANGE VALUE OF METEORITES. 525 



last quoted medium trade prices, is 75 cents, and their average 

 Wulfing price is $2.20. Thus on stones not seen to fall, Wiilfing 

 estimates atout three times the market value. 



6. Area of Slice. — According to Cohen, a section of relatively 

 large exhibition area is of more value per gram than a thicker piece 

 of the same weight. Of two pieces of the same weight, the one 

 having the larger exhibition surface will be chosen, as better illus- 

 trating the variation in structure, crystallization and included 

 minerals, besides making a more impressive display. However, 

 most 1912 catalogues show no apparent difference in the price per 

 gram because of differences in thickness. While there is little 

 advantage in a slice of iron 20 to 30 cm. broad being more than 

 I cm. thick, some siderolites and aerolites require a greater thick- 

 ness because of their friability. Quite apart from the relative de- 

 sirability of two pieces of the same weight but of differing exhibi- 

 tion area, is the large item of cost, since a thin slice costs propor- 

 tionately more per gram for sawing and wastage than a thick slice. 



7. Phenomenal Variation between Individual Specimens. — In- 

 teresting differences between individual slices or masses of the same 

 fall are often seen. In aerolites, one fragment or slice may (i) 

 have much more crust than another; (2) it may show a slickensided 

 surface; (3) primary and secondary crust formed before and after 

 exploding; (4) radial lines of fusion flow on the front, with thicker 

 overflow on back; (5) brecciation, etc. In irons, one slice may (i) 

 rarely show hieroglyphic characters and often nodules of included 

 iron compounds; (2) twinning; (3) a flowage of the usually 

 straight Widmanstatten figures; (4) on the exterior deep pitting, or 

 fluidal lines; (5) more commonly, marked octahedral cleavage. 

 Such features increase the value of one piece over that of another 

 of the same weight and fall which is less interestingly marked. An 

 extreme case is Canyon Diablo, valued at 3 cents per gram. When 

 showing diamonds (of no commercial value), the price has exceeded 

 30 cents per gram. 



8. Distinctness of Structure. — Other things being equal, beauti- 

 fully crystallized irons and stones of striking chondritic structure, 

 are prized higher than those in which the crystallization is clouded 

 or the structure quite indistinct. 



