52 THE GRANITES OF MAINE. 
quarrymen as w * iron seams/ 1 At the Bryant Pond quarry (see p. 
146) one of the joints is coated with calcite (with a little epidote and 
pyrite) up to half an inch in thickness, and the granite on either 
side contains considerable chlorite, derived probably from the 
alteration of its hornblende. A muscovite-biotite granite quarried 
at Oxford (p 140) has considerable secondary muscovite developed 
along - planes which appear to be due to close jointing. At the 
McMullen quarry, on Somes Sound, Mount Desert, the light bull' 
and white feldspar is altered for the width of a foot along the steep 
joints to a deep reddish color. This change does not occur along 
the sheets. A thin section of this red feldspar shows that the color 
affects both potash and soda-lime feldspars alike and is due to innu- 
merable dots of infinitesimal size, but without definite form or color 
under the higher powers of the microscope. They are probably 
hematite. 
It seems probable that the calcite and pyrite are infiltrations from 
calcareous and ferruginous formations that once overlay the granite, 
but were subsequently eroded." 
The presence of epidote, chlorite, muscovite, stilbite, pyrite, and 
hematite in or near joint faces may be attributed to a process of deep- 
seated mineral alteration aided by percolating waters, which took up 
some elements and deposited others, and were also probably under 
pressure. These changes may have occurred subsequent to the intru- 
sion of the diabase dike-, because the dikes also have suffered similar 
alteration. 
DISCOLORA [TON I " SAT." ETC.). 
Rusty (limonite) staining along the upper and lower parts of the 
sheets and also along the joints and headings is common in granite 
quarries, although some quarries are almost entirely free from it. 
The concentric inward growth of "sap*' from the close joints of a 
heading is well shown in PL IX, B. The zone of discoloration along 
the sheets in the Maine quarries is from one-half to 12 inches, excep- 
tionally even IS inches, wide on each side of the sheet parting. It> 
width, however, decreases gradually from the surface sheets down- 
ward. In places the sap consists of two parts — an outer dark brown- 
ish zone from three-fourths to \\ inches wide and an inner mon 
yellowish zone from one-fourth to one-half inch wide. Generally 
however, the discoloration diminishes gradually from without inward 
In some quarries there seems to be a connection between the " shake' 
structure (p. 150) and the discoloration, since these are coextensive. 
When the stone is intended for facing or trimming buildings th< 
"One-fourth of a mile cast of Fori Ann. in Washington County, X. V.. Professor Kern 
and the writer observed open vertical joints in the pre-Cambrian noncalcareous gneis 
filled with calcite, evidently derived from an extraneous source, 
