180 CONTRIBUTIONS TO THE GEOLOGY OF MAINE. [bttll,165. 
ever, and no line of demarcation is possible between the different 
phases. The teschenites are readily decomposed by weathering, break- 
ing down in place to a fine, brown sand, which accounts for the absence 
of sharp cliff ledges at the outcrops and makes it difficult to secure 
unaltered material. Even the specimens obtained by blasting, which 
appeared beautifully fresh in the field, were found by examination of 
thin sections to contain many altered minerals. 
In the following description the varieties obtained will, for the sake 
of simplicity, be grouped under three heads: 'the coarse crystalline 
type, the granular type, and the contact facies. For a map of this 
district see page 116. 
COARSE CRYSTALLINE TYPE. 
This constitutes nearly all the great dike on lot 100 and the outcrop 
at the northeast corner of lot 107. 
Macroscopic description. — Typical hand specimens show a rock made 
of a mixture of white or pink and lustrous black materials in about 
equal quantities, but with a tendency toward aggregation of like parts 
which makes dark and light areas. The light parts are composed of 
white or pink feldspars, in the midst of which are good-sized areas of 
milk-white analcite. The dark parts are composed of black augite 
mingled with grains of magnetite. Masses of oily green chloritic 
material are also macroscopically apparent. The crystals will average 5 
to 6 millimeters in largest diameter. From this type, in which the dark 
and light components appear equally represented, there is a variation 
on the one hand to a black crystalline aggregate of augite and iron, 
and on the other to a tangled mass of feldspar laths, filling the inter- 
spaces and containing black minerals without definite outlines. One 
feldspathic variety is unique in some particulars. It is composed 
largely of good-sized, perfectly formed pink feldspar, with shining 
cleavage faces and with the f erromagnesian minerals wanting or reduced 
to inconspicuous grains. The rock is much weathered and shows 
numerous irregular cavities, from which some mineral has been removed 
and which are now lined with black dust or rarely filled with calcite. 
Such cavities are found also in weathered parts of the other varieties. 
Microscopic description. — Several slides of this coarse type of the 
teschenites were prepared, none of which showed all the minerals in 
good condition, but the character of each was very well made out by aji 
comparative study. The minerals present in the order of their forma- 
tion are: Black iron ore, with a few grains of pyrite; apatite, biotite, 
feldspar, augite, and analcite. This order, however, is not strictly 
observed, and the appearance is more as if several minerals had been 
crystallizing simultaneously. The iron ore is largely magnetite and is 
very abundant in the section as partly formed polygons or irregular 
