MINERALOGY: G. P. MERRILL 
179 
ameter, were introduced into pits bored in fire-brick, and sealed up with fire- 
clay. These bricks were then placed on top of a gas-fuel zienc smelter, where 
they were allowed to remain for a period of four months, and in an atmosphere 
in which oxidizing influences were reduced to a minimum. The exact tem- 
perature could not be determined, but a cube of the Casas Grandes iron in 
one of the pits was completely fused and absorbed into one of the bricks, 
indicating a temperature not less than 1450°C. The results on the two stones 
were as follows: 
Estacado, Texas. — This, a veined crystalline chondrite of a dark gray color, 
fine and compact texture, consists essentially of olivine and enstatite with 
smaller amounts of pyrrhotite and nickel-iron. Before heating, the silicates 
are colorless and limpid, and the metallic constituents scattered in small gran- 
ules fairly uniformly throughout the mass. The roasting resulted in producing 
a slight glaze on the exterior surface of the cube. The color was much dark- 
ened, becoming uniformly dull black. Although remaining firm and hard, 
the stone became filled with fine vesicles. The thin section under the micro- 
scope seemed at first completely amorphous. In strong sunlight, however, 
the silicates, although nearly opaque and without action in polarized light, 
were of a deep dull red, indicating a certain amount of oxidation of the iron. 
The interstices were filled with a fine, dust4ike, opaque and amorphous matter 
which is impossible of determination. The particles of metal had been fused 
and the material diffused throughout the ground to appear in the form of 
minute blue points in reflected light. With the exception of the metal not a 
single one of the original constituents was recognizable. 
Homestead, Iowa. — This is a dark gray, homogeneous, hard and firm stone 
belonging to Brezina's brecciated gray chondrite group. The mineral com- 
position, as determined by Wadsworth, is olivine, enstatite, pyrrhotite, iron, 
and base. Lasaulx is quoted as having noted the occurrence of a feldspar. 
I find, in addition, a polysynthetically twinned pyroxene and a calcium phos- 
phate in small quantities. After the roasting, the color is dull black and the 
texture finely vesicular, although firm and hard. As was the case with the 
Estacado stone, it is so opaque in thin sections as to almost entirely obscure 
its original structure. The silicates are altered in the same manner, though 
the olivine is the most affected; the metal is likewise diffused, and attempts 
at making a photo-micrograph from the slides resulted in complete failure. 
As it was evident the experiment had been carried too far a second attempt 
was made in the museum laboratory at lower temperatures and for shorter 
periods. 
Small pieces of the Homestead meteorite, of 2 or 3 grams weight, were 
roasted in a covered crucible at a low red heat for periods of one-half and one 
hour each, the gas flame playing freely up and around the crucible. The 
external manifestations of this heating were a change in color to dark gray 
and a fusion, on the outer surface, of the troilite granules. A thin section 
showed the nickel-iron to be unchanged, though the troilite had been broken 
