180 
MINERALOGY: G. P. MERRILL 
up to a greater or less extent. The principal change lay in the finer siliceous 
material occupying the interstices of the other minerals which had turned, in 
part, black and amorphous. A like change had taken place along the borders 
of the chondrules and cleavage and fracture lines of the larger phenocryst, 
giving them the appearance of having been injected with, some dark coloring 
fluid. The amount of change was proportional to the length of time in heating, 
as shown in figures 1, 2 and 3. 
Figure 1 is from the unaltered stone and 2 and 3 from fragments heated 
for one half and one hour respectively. It will be noted that there is an in- 
crease in the amount of black opaque matter in 2 and 3 over that in 1. In the 
piece roasted for a full hour the fine interstitial silicates have become wholly 
changed to the black matter which penetrates the borders of the chondrules and 
other crystal aggregates, until a condition is reached so closely resembling 
that shown in sections of the McKinney (fig. 4) and Travis County (fig. 5) 
black chondrites as to apparently leave no doubt as to the correctness of 
Meunier's view to the effect that such are but phases of chondritic stones 
which have been altered through a re-heating subsequent to their first crystal- 
lization. It should be added that these roasted pieces are partially restored 
to their original color by digestion in hydrochloric acid and sodium car- 
bonate, showing that the change is one that has influenced chiefly the olivine. 
Incidentally attention may well be called to the manner in which the blacken- 
ing of the stone first manifests itself along cleavage and fracture lines in 
figure 5. 
It should be noted further that it is doubtful if all of the dark color in these 
black chondrules is due to roasting, since some of them heated in a closed 
tube give evidence of the presence of a small amount of a hydrocarbon. 
1 Encyclopedic Chimique, 2, appendix 2, Meteorites. 
2 Amer. J. Sci., New Haven, 43, 1918, (322). 
*Ibid., 49, 1895, (101-110). 
4 See my papers on the meteorites of Holbrook, Arizona, Smithsonian Misc. Coll., Wash- 
ington, 60, No. 9, 1912; Modoc, Kansas, Amer. J. Sci., New Haven, 21, 1906, (356-360); 
Rich Mountain, North Carolina, Proc. U. S. Nat. Mus., Washington, 32, 1907, (241-244); 
Thomson, Georgia, Smithsonian Misc. Coll., 52, 1909, (473-476); Fisher, Minnesota, Proc. 
U. S. Nat. Mus., 48, 1915, (503-506); and Coon Butte, Arizona, (Mallet), Amer. J. Sci., 
21, 1906, (351). 
5 See Cohen's Meleoritenkunde, pp. 311-314, Figure 2 on plate 17 or Tschermak's Die 
Mikroskopische Beschafenheit der Meteoriten will apply equally well to the majority of 
occurrences. 
