QUARRIES IN LINCOLN COUNTY. 139 
LINCOLN COUNTY. 
The quarries in Lincoln County are in the towns of Bristol, Waldo- 
>oro, and Whitefield. 
The Round Pond quarry is in the town of Bristol, one-fourth mile 
sast of Round Pond village, and west of Muscongus Island. Opera- 
tor, Peter Swensen & Co., Round Pond, Me. 
The rock (specimens 126 «, 126 b) is a quartz diorite of very dark 
rray and medium-gray shades and of fine, even-grained texture, with 
feldspars up to one-fifth inch. The darker variety consists, in 
lescending order of abundance, of bluish-white soda-lime feldspar 
oligoclase-andesine), clear quartz, black mica (biotite), potash 
? eldspar (orthoclase and microcline), and magnetite, together with 
iccessory titanite, zircon, apatite, and secondary calcite. The lighter 
consists of the same minerals, but with less biotite, so that it changes 
pace with the potash feldspar in order of abundance. Both varie- 
ies take a fine polish and offer a very marked contrast between the 
Dolished and cut or hammered surface. Granite of the same shade 
iffords no such contrast. 
The quarry, opened in 1885, consists of two adjacent openings 
ilong a northwest-southeast line. The upper or northwestern one is 
.00 feet square; the lower is 400 feet (northwest-southeast) by 100 feet 
icross, but with a central part 37 feet wide on each side — that is, 175 
'eet wide. These openings range in depth from 10 to 65 feet. Drain- 
ige is natural, the excavations not having gone below high-tide level. 
Rock structure: Considerable scientific interest attaches to the 
geological relations at this quarry, as may be seen by the references 
;o them on pages 44, 48, 60-62. This quarry has been described by 
F. E. Wolff. a The diorite underlies a mass of schist which strikes 
ST* 15° E., and is traversed by dikes and lenses of coarse pegmatite, 
[t also includes a tongue of this schist, as shown in PL XI, B, and is 
traversed by dikes of pegmatite, as shown in PL X, i?, and XI, A, 
md itself, in turn, is traversed, as is also its pegmatite, by a diabase 
like. Thus the schists are older than the diorite, and the dike is later 
;han the diorite and its pegmatite. The joint and dike courses are 
shown in fig. 28. The sheets, from 1 to 12 feet thick, dip 10° south 
md also 10° east, and are traversed by joints A, which recur at inter- 
nals of 5 to 42 feet, and B, which recur but once or twice. There are 
}ad headings on the northeast side of the quarry. The pegmatite 
likes send out small branches. Sap, only 1 inch thick, occurs along 
:he sheets. Knots measure up to 6 by 2 inches, but are rare. These 
sheets, joints, and dikes are shown in the plates referred to. The gen- 
eral result of this complex structure is that it is difficult to obtain 
nany large blocks. 
Details of Maine granite quarries: Tenth Census, vol. 10, 1888, p. 121. 
