122 THE GRANITES OF MAINE. 
KNOX COUNTY. 
The quarries in Knox County are in Muscle Ridge Plantation and 
the towns of St. George, South Thomaston, Tenants Harbor, and 
Vinalhaven. 
The High Isle quarry is in Muscle Ridge Plantation, 9J miles south- 
southeast of Rockland. Operator, William Gray & Son; office. Thir- 
tieth street, beloAv Walnut, Philadelphia, Pa. 
The granite (specimen 18, a) is a biotite granite of slightly pinkish 
medium-gray color, with conspicuous black mica and of medium to 
coarse, even-grained texture, the feldspars measuring up to one-half 
inch and most of the biotite scale- up to one-tenth inch, but some one- 
fifth inch. It consists, in descending order of abundance, of a delicate 
pink potash feldspar (orthoclase and microcline), smoky quartz, 
milk-white (very slightly bluish) soda-lime feldspar (oligoclase), 
and black mica (biotite). together with accessory magnetite, apatite, 
and secondary chlorite. The oligoclase is in some places partially 
altered to a white mica. The contrasts between the minerals are rather 
marked, but the polish is not very satisfactory, owing to the large 
size of the biotite scales. 
The following chemical analysis and determination of specific 
gravity were made for the firm by Prof. James F. Kemp, E. M., of. 
Columbia University : 
Analysis of granite from quarry <it High Isle quarry. 
SiO, (silica) 74.54 
A1 2 3 (alumina) L3. 30 
FeO (ferrous oxide) <>. 7!> 
Fe 2 3 (ferric oxide) 0. 92 
CaO (lime) 1.2G 
MgO (magnesia) 0.009 
Mil (manganese) 0. 51 ] 
S (sulphur) 0.038 
Na 2 (soda) 3.69 
K 2 U (potash) 5.03 
100. 0G7 
Loss on ignition, 0.55. 
Specific gravity, 2.641, equal to 165.00 pounds per cubic foot. 
The results of four crushing tests on cubes (2-inch) bedded with 
plaster of* Paris, made at the engineering laboratory of Columbia 
University for the firm, are as follows: First crack at 100,000 to 
126,300 pounds. Ultimate strength in pounds per square inch, 25,880, 
32,360,32,495,33,085. (Laboratory Xos. L759 to 1761.) 
The quarry, opened about 1894, consists of five openings, each about 
100 feet square, with a maximum depth of 50 feet and an average 
