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BULLETIN OF THE LABORATORIES 
thoclase in Carlsbad twins, is more frequently fractured than rounded 
and is often filled with tongues of interpenetrating magma. This 
magma is beautifully fluidal, the dark ingredients (biotite, chiefly al- 
tered to chlorite) are scattered in crevices of the feldspars or sheltered 
spots behind them where they have drifted like float-wood. 
No. 1009, from the bands, is essentially similar, but is much finer- 
grained and has fewer and smaller porphyritic ingredients. There are 
mica rosettes and groups of magnetite, pyrite, apatite and other acces- 
sories, as well as veins of calcite. • 
No. loii. Chloritic schist one-half to three-fourths of a mile N. 
E. of Dog river. It is greatly contorted, unctuous, containing large 
quantities of calcite in the form of veins which conform to the contor- 
tion. Microscopically it appears to be composed of a ground mass of 
chlorite scales which when reduced to very thin sections lose their po- 
larization colors and pleochroism. This ground mass is filled with 
large crystals of much altered orthoclase, which have a tendency to 
aggregate at 90° to axis c. The titanic iron shows all the gradations 
to titanite. Large calcite grains showing characteristic cleavage in 
three directions, with banded structure. The crystals of apatite pene- 
trate all the ingredients of the rock. The rock appears to be much 
altered from the influence of the interpenetrating diabase dykes. 
Here as in other places it seems as if the interpenetrating dykes com- 
ing through the primitive schists had fused the lower portions which 
oozed up along the sides of the dyke and in cooling formed the more 
coarsely crystalline rock No. 1012. (Plate XII, Figs, i, 2, and 3.) 
No. 1012. Dark gray, coarse grained, unevenly fracturing rock, 
intersected in all directions by veins of various minerals. Microscop- 
ically it appears coarsely crystalline, with orthoclase and plagioclase 
magma. The rock contains a considerable amount of biotite, some 
calcite and a very few grains of hematite, with crystals of apatite scat- 
tered through it sparingly. It appears as if this rock was the slowly 
cooled product of the fused lower portion of the schists in which mica 
and plagioclase have crystalized out. This all, apparently, through the 
influence of the dyke which comes up through this boss and forms 
No. 1013. 
No. T013. A fine grained dark rock presenting all the characters 
of a typical diabase. The line of contact with No. 12 is very sharply 
marked. 
