lg THE GRANITES OF MAINE. 
besides the carbonate. It is probably safe to assume that the acetic 
acid has not attacked the biotite." 
During the preparation of this report the accessory minerals gar- 
net, zircon, titanite, magnetite, pyrite, apatite, and molybdenite have 
been found in Maine granites. Allanite also is reported.. 
A white silicate which occurs in the Waldoboro granite in isolated 
more or less incomplete crystals, some of them as much as half an 
inch in diameter, and which becomes slightly yellowish on weather- 
ing, has been determined by Dr. George P. Merrill, of the United 
States National Museum, as a feldspar between oligoclase and albite. 
The feldspar of that granite is. however, oligoclase. 
The arrangement of the important minerals in the stone will be 
described under the heading "Texture." 
The percentages of the mineral constituents differ within wide 
limits in granites from different localities. 'The percentage of mus- 
covite and of the ferromagnesian minerals (biotite, hornblende, 
augite) is always small, while that of the feldspar and quartz i> large. 
There is considerable variation in the relative amounts of feldspar 
and quartz and still more in the amounts of each of the feldspars. 
The reddish color of the feldspar— a color that plays an important 
part in the appearance of the stone — is due to an amount of ferrous 
oxide which rarely exceeds 1 per cent of the mineral and which under 
the highest powers of the microscope shows no definite form. 
CHEMICAL COMPOSITION. 
The chemical composition of granite is of Less scientific and eco- 
nomic significance than its mineral composition, for, although chem- 
ical analysis shows the percentages of the constituent elements, the 
process by which these are determined necessarily mingles the ele- 
ments of several minerals whose proportions vary and whose con- 
tribution to the physical properties of the rock differ greatly. When, 
however, a combination of elements occurs only in one or two of the 
minerals the chemical analysis serves to corroborate the evidence 
obtained by microscopic analysis. 
Many analyses of granite have been published, but it will suffice 
here to give the extremes of the percentages shown by some of the 
more important of these and to refer the reader to works containing 
complete analyses.** Four analyses of granites from Scotland, Ire- 
land, Italy, and Sweden show the following ranges : & 
" See Washington, II. S.. Prof. Papers r. S. Geol. Survey Nos. 14, 1003, and 28, 1004; 
also Clarke, F. W., Bull. U. S. Geol. Survey No. 228, L904. 
Hieikie, Archibald, Text-book of Geology, in, -.1.. vol. 1, London, 1903, p. 207. 
